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	$65.58	12.686%	$73.8995	$73.90	$73.90	$73.90
Purchase #2	$40.32	8.238%	$43.6416	$43.64	$43.65	$43.60
Purchase #3	$36.68	3.303%	$37.8915	$37.89	$37.90	$37.90
Purchase #4	$41.78	10.752%	$46.2722	$46.27	$46.25	$46.30
Purchase #5	$179.57	3.315%	$185.5227	$185.52	$185.50	$185.50
Purchase #6	$111.53	11.617%	$124.4864	$124.49	$124.50	$124.50
Purchase #7	$85.74	12.428%	$96.3958	$96.40	$96.40	$96.40
7 purchase totals =	$561.20		$608.1097	$608.11	$608.10	$608.10