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	$222.59	7.396%	$239.0528	$239.05	$239.05	$239.10
Purchase #2	$124.74	4.607%	$130.4868	$130.49	$130.50	$130.50
Purchase #3	$198.48	12.646%	$223.5798	$223.58	$223.60	$223.60
Purchase #4	$100.85	8.620%	$109.5433	$109.54	$109.55	$109.50
Purchase #5	$38.39	3.323%	$39.6657	$39.67	$39.65	$39.70
Purchase #6	$145.92	10.618%	$161.4138	$161.41	$161.40	$161.40
Purchase #7	$107.90	4.870%	$113.1547	$113.15	$113.15	$113.20
7 purchase totals =	$938.87		$1,016.8969	$1,016.89	$1,016.90	$1,017.00