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	$96.66	3.873%	$100.4036	$100.40	$100.40	$100.40
Purchase #2	$34.73	6.403%	$36.9538	$36.95	$36.95	$37.00
Purchase #3	$224.88	3.227%	$232.1369	$232.14	$232.15	$232.10
Purchase #4	$152.42	9.405%	$166.7551	$166.76	$166.75	$166.80
Purchase #5	$148.77	6.761%	$158.8283	$158.83	$158.85	$158.80
Purchase #6	$105.75	5.752%	$111.8327	$111.83	$111.85	$111.80
Purchase #7	$195.70	10.682%	$216.6047	$216.60	$216.60	$216.60
7 purchase totals =	$958.91		$1,023.5151	$1,023.51	$1,023.55	$1,023.50