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	$88.69	8.237%	$95.9954	$96.00	$96.00	$96.00
Purchase #2	$249.65	10.785%	$276.5748	$276.57	$276.55	$276.60
Purchase #3	$222.82	8.801%	$242.4304	$242.43	$242.45	$242.40
Purchase #4	$69.57	4.269%	$72.5399	$72.54	$72.55	$72.50
Purchase #5	$81.25	5.416%	$85.6505	$85.65	$85.65	$85.70
Purchase #6	$106.36	7.439%	$114.2721	$114.27	$114.25	$114.30
Purchase #7	$237.69	10.575%	$262.8257	$262.83	$262.85	$262.80
7 purchase totals =	$1,056.03		$1,150.2888	$1,150.29	$1,150.30	$1,150.30