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	$20.32	9.500%	$22.2504	$22.25	$22.25	$22.30
Purchase #2	$130.65	12.655%	$147.1838	$147.18	$147.20	$147.20
Purchase #3	$90.57	9.234%	$98.9332	$98.93	$98.95	$98.90
Purchase #4	$78.89	6.677%	$84.1575	$84.16	$84.15	$84.20
Purchase #5	$239.71	6.758%	$255.9096	$255.91	$255.90	$255.90
Purchase #6	$232.57	4.634%	$243.3473	$243.35	$243.35	$243.30
Purchase #7	$238.99	8.839%	$260.1143	$260.11	$260.10	$260.10
7 purchase totals =	$1,031.70		$1,111.8961	$1,111.89	$1,111.90	$1,111.90