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	$191.83	8.511%	$208.1567	$208.16	$208.15	$208.20
Purchase #2	$85.42	11.629%	$95.3535	$95.35	$95.35	$95.40
Purchase #3	$209.59	5.677%	$221.4884	$221.49	$221.50	$221.50
Purchase #4	$152.39	12.771%	$171.8517	$171.85	$171.85	$171.90
Purchase #5	$143.39	10.298%	$158.1563	$158.16	$158.15	$158.20
Purchase #6	$216.84	9.416%	$237.2577	$237.26	$237.25	$237.30
Purchase #7	$53.63	12.390%	$60.2748	$60.27	$60.25	$60.30
7 purchase totals =	$1,053.09		$1,152.5391	$1,152.54	$1,152.50	$1,152.80