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	$215.66	5.774%	$228.1122	$228.11	$228.10	$228.10
Purchase #2	$34.79	8.312%	$37.6817	$37.68	$37.70	$37.70
Purchase #3	$218.41	4.759%	$228.8041	$228.80	$228.80	$228.80
Purchase #4	$117.76	8.320%	$127.5576	$127.56	$127.55	$127.60
Purchase #5	$38.69	12.543%	$43.5429	$43.54	$43.55	$43.50
Purchase #6	$140.38	12.664%	$158.1577	$158.16	$158.15	$158.20
Purchase #7	$131.58	11.380%	$146.5538	$146.55	$146.55	$146.60
7 purchase totals =	$897.27		$970.4100	$970.40	$970.40	$970.50