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	$190.52	12.588%	$214.5027	$214.50	$214.50	$214.50
Purchase #2	$189.85	8.304%	$205.6151	$205.62	$205.60	$205.60
Purchase #3	$74.46	6.796%	$79.5203	$79.52	$79.50	$79.50
Purchase #4	$44.27	13.790%	$50.3748	$50.37	$50.35	$50.40
Purchase #5	$209.32	6.284%	$222.4737	$222.47	$222.45	$222.50
Purchase #6	$164.28	6.456%	$174.8859	$174.89	$174.90	$174.90
Purchase #7	$182.73	11.164%	$203.13	$203.13	$203.15	$203.10
7 purchase totals =	$1,055.43		$1,150.5025	$1,150.50	$1,150.45	$1,150.50