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	$190.55	7.244%	$204.3534	$204.35	$204.35	$204.40
Purchase #2	$102.87	4.190%	$107.1803	$107.18	$107.20	$107.20
Purchase #3	$179.89	9.114%	$196.2852	$196.29	$196.30	$196.30
Purchase #4	$118.98	11.635%	$132.8233	$132.82	$132.80	$132.80
Purchase #5	$166.28	7.833%	$179.3047	$179.30	$179.30	$179.30
Purchase #6	$44.28	9.132%	$48.3236	$48.32	$48.30	$48.30
Purchase #7	$120.78	11.696%	$134.9064	$134.91	$134.90	$134.90
7 purchase totals =	$923.63		$1,003.1769	$1,003.17	$1,003.15	$1,003.20