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	$174.41	11.389%	$194.2736	$194.27	$194.25	$194.30
Purchase #2	$99.37	8.854%	$108.1682	$108.17	$108.15	$108.20
Purchase #3	$200.61	10.566%	$221.8065	$221.81	$221.80	$221.80
Purchase #4	$143.91	6.103%	$152.6928	$152.69	$152.70	$152.70
Purchase #5	$156.85	9.825%	$172.2605	$172.26	$172.25	$172.30
Purchase #6	$205.58	11.592%	$229.4108	$229.41	$229.40	$229.40
Purchase #7	$78.84	9.132%	$86.0397	$86.04	$86.05	$86.00
7 purchase totals =	$1,059.57		$1,164.6521	$1,164.65	$1,164.60	$1,164.70