Let's do some math ..  Rounding examples of 7 random hypothetical purchases:
Case	Tag   Price	Sales   Tax %	Raw Total   Incl. Sales Tax	Rounded   to Penny	Rounded   to Nickel	Rounded   to Dime
Purchase #1	$102.57	8.775%	$111.5705	$111.57	$111.55	$111.60
Purchase #2	$181.89	12.587%	$204.7845	$204.78	$204.80	$204.80
Purchase #3	$139.76	8.704%	$151.9247	$151.92	$151.90	$151.90
Purchase #4	$248.36	10.379%	$274.1373	$274.14	$274.15	$274.10
Purchase #5	$170.93	10.574%	$189.0041	$189.00	$189.00	$189.00
Purchase #6	$145.43	10.108%	$160.1301	$160.13	$160.15	$160.10
Purchase #7	$96.25	13.705%	$109.4411	$109.44	$109.45	$109.40
7 purchase totals =	$1,085.19		$1,200.9923	$1,200.98	$1,201.00	$1,200.90