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	$151.42	11.207%	$168.3896	$168.39	$168.40	$168.40
Purchase #2	$146.66	4.144%	$152.7376	$152.74	$152.75	$152.70
Purchase #3	$243.76	7.534%	$262.1249	$262.12	$262.10	$262.10
Purchase #4	$90.36	11.458%	$100.7134	$100.71	$100.70	$100.70
Purchase #5	$30.78	4.145%	$32.0558	$32.06	$32.05	$32.10
Purchase #6	$239.68	10.337%	$264.4557	$264.46	$264.45	$264.50
Purchase #7	$45.58	9.771%	$50.0336	$50.03	$50.05	$50.00
7 purchase totals =	$948.24		$1,030.5106	$1,030.51	$1,030.50	$1,030.50