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	$127.64	10.379%	$140.8878	$140.89	$140.90	$140.90
Purchase #2	$195.44	6.540%	$208.2218	$208.22	$208.20	$208.20
Purchase #3	$130.69	5.154%	$137.4258	$137.43	$137.45	$137.40
Purchase #4	$157.91	11.311%	$175.7712	$175.77	$175.75	$175.80
Purchase #5	$107.96	6.502%	$114.9796	$114.98	$115.00	$115.00
Purchase #6	$54.51	8.433%	$59.1068	$59.11	$59.10	$59.10
Purchase #7	$70.81	10.323%	$78.1197	$78.12	$78.10	$78.10
7 purchase totals =	$844.96		$914.5127	$914.52	$914.50	$914.50