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	$166.68	9.414%	$182.3713	$182.37	$182.35	$182.40
Purchase #2	$117.69	4.643%	$123.1543	$123.15	$123.15	$123.20
Purchase #3	$127.33	11.150%	$141.5273	$141.53	$141.55	$141.50
Purchase #4	$142.36	12.606%	$160.3059	$160.31	$160.30	$160.30
Purchase #5	$222.74	13.516%	$252.8455	$252.85	$252.85	$252.80
Purchase #6	$225.37	4.798%	$236.1833	$236.18	$236.20	$236.20
Purchase #7	$6.34	11.792%	$7.0876	$7.09	$7.10	$7.10
7 purchase totals =	$1,008.51		$1,103.4752	$1,103.48	$1,103.50	$1,103.50