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	$143.77	9.663%	$157.6625	$157.66	$157.65	$157.70
Purchase #2	$79.66	13.785%	$90.6411	$90.64	$90.65	$90.60
Purchase #3	$203.74	11.675%	$227.5266	$227.53	$227.55	$227.50
Purchase #4	$193.55	5.654%	$204.4933	$204.49	$204.50	$204.50
Purchase #5	$83.70	3.604%	$86.7165	$86.72	$86.70	$86.70
Purchase #6	$80.53	11.647%	$89.9093	$89.91	$89.90	$89.90
Purchase #7	$151.84	6.300%	$161.4059	$161.41	$161.40	$161.40
7 purchase totals =	$936.79		$1,018.3552	$1,018.36	$1,018.35	$1,018.30