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	$139.80	10.772%	$154.8593	$154.86	$154.85	$154.90
Purchase #2	$60.63	7.835%	$65.3804	$65.38	$65.40	$65.40
Purchase #3	$30.85	4.522%	$32.245	$32.25	$32.25	$32.20
Purchase #4	$61.67	5.154%	$64.8485	$64.85	$64.85	$64.80
Purchase #5	$72.52	8.424%	$78.6291	$78.63	$78.65	$78.60
Purchase #6	$209.85	11.363%	$233.6953	$233.70	$233.70	$233.70
Purchase #7	$24.62	9.114%	$26.8639	$26.86	$26.85	$26.90
7 purchase totals =	$599.94		$656.5215	$656.53	$656.55	$656.50