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	$197.64	12.812%	$222.9616	$222.96	$222.95	$223.00
Purchase #2	$24.52	10.810%	$27.1706	$27.17	$27.15	$27.20
Purchase #3	$52.70	8.559%	$57.2106	$57.21	$57.20	$57.20
Purchase #4	$167.70	4.538%	$175.3102	$175.31	$175.30	$175.30
Purchase #5	$157.64	6.581%	$168.0143	$168.01	$168.00	$168.00
Purchase #6	$196.30	5.342%	$206.7863	$206.79	$206.80	$206.80
Purchase #7	$80.58	11.552%	$89.8886	$89.89	$89.90	$89.90
7 purchase totals =	$877.08		$947.3422	$947.34	$947.30	$947.40