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	$172.74	6.796%	$184.4794	$184.48	$184.50	$184.50
Purchase #2	$181.62	12.138%	$203.665	$203.67	$203.65	$203.70
Purchase #3	$139.50	6.304%	$148.2941	$148.29	$148.30	$148.30
Purchase #4	$27.63	4.654%	$28.9159	$28.92	$28.90	$28.90
Purchase #5	$164.84	12.609%	$185.6247	$185.62	$185.60	$185.60
Purchase #6	$37.96	11.864%	$42.4636	$42.46	$42.45	$42.50
Purchase #7	$208.58	3.115%	$215.0773	$215.08	$215.10	$215.10
7 purchase totals =	$932.87		$1,008.5200	$1,008.52	$1,008.50	$1,008.60