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	$57.53	4.603%	$60.1781	$60.18	$60.20	$60.20
Purchase #2	$234.89	7.225%	$251.8608	$251.86	$251.85	$251.90
Purchase #3	$167.56	9.141%	$182.8767	$182.88	$182.90	$182.90
Purchase #4	$95.93	3.342%	$99.136	$99.14	$99.15	$99.10
Purchase #5	$222.41	11.158%	$247.2265	$247.23	$247.25	$247.20
Purchase #6	$215.87	4.597%	$225.7935	$225.79	$225.80	$225.80
Purchase #7	$150.76	10.608%	$166.7526	$166.75	$166.75	$166.80
7 purchase totals =	$1,144.95		$1,233.8242	$1,233.83	$1,233.90	$1,233.90