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	$192.57	10.185%	$212.1833	$212.18	$212.20	$212.20
Purchase #2	$35.73	13.537%	$40.5668	$40.57	$40.55	$40.60
Purchase #3	$133.75	11.323%	$148.8945	$148.89	$148.90	$148.90
Purchase #4	$64.91	4.417%	$67.7771	$67.78	$67.80	$67.80
Purchase #5	$245.36	12.305%	$275.5515	$275.55	$275.55	$275.60
Purchase #6	$229.74	13.726%	$261.2741	$261.27	$261.25	$261.30
Purchase #7	$61.62	9.597%	$67.5337	$67.53	$67.55	$67.50
7 purchase totals =	$963.68		$1,073.7810	$1,073.77	$1,073.80	$1,073.90