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	$229.71	3.852%	$238.5584	$238.56	$238.55	$238.60
Purchase #2	$86.89	11.358%	$96.759	$96.76	$96.75	$96.80
Purchase #3	$20.27	6.413%	$21.5699	$21.57	$21.55	$21.60
Purchase #4	$128.58	6.500%	$136.9377	$136.94	$136.95	$136.90
Purchase #5	$250.56	5.536%	$264.431	$264.43	$264.45	$264.40
Purchase #6	$104.93	10.588%	$116.04	$116.04	$116.05	$116.00
Purchase #7	$104.37	8.420%	$113.158	$113.16	$113.15	$113.20
7 purchase totals =	$925.31		$987.4540	$987.46	$987.45	$987.50