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	$152.57	4.217%	$159.0039	$159.00	$159.00	$159.00
Purchase #2	$28.66	11.470%	$31.9473	$31.95	$31.95	$31.90
Purchase #3	$111.92	13.801%	$127.3661	$127.37	$127.35	$127.40
Purchase #4	$59.77	12.287%	$67.1139	$67.11	$67.10	$67.10
Purchase #5	$168.48	3.472%	$174.3296	$174.33	$174.35	$174.30
Purchase #6	$134.90	11.569%	$150.5066	$150.51	$150.50	$150.50
Purchase #7	$195.43	5.563%	$206.3018	$206.30	$206.30	$206.30
7 purchase totals =	$851.73		$916.5692	$916.57	$916.55	$916.50