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	$142.91	4.189%	$148.8965	$148.90	$148.90	$148.90
Purchase #2	$163.77	13.532%	$185.9314	$185.93	$185.95	$185.90
Purchase #3	$72.95	7.657%	$78.5358	$78.54	$78.55	$78.50
Purchase #4	$182.85	13.133%	$206.8637	$206.86	$206.85	$206.90
Purchase #5	$134.74	13.140%	$152.4448	$152.44	$152.45	$152.40
Purchase #6	$227.84	7.428%	$244.764	$244.76	$244.75	$244.80
Purchase #7	$85.40	8.521%	$92.6769	$92.68	$92.70	$92.70
7 purchase totals =	$1,010.46		$1,110.1131	$1,110.11	$1,110.15	$1,110.10