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	$206.61	4.124%	$215.1306	$215.13	$215.15	$215.10
Purchase #2	$105.69	5.754%	$111.7714	$111.77	$111.75	$111.80
Purchase #3	$201.81	8.700%	$219.3675	$219.37	$219.35	$219.40
Purchase #4	$245.53	5.144%	$258.1601	$258.16	$258.15	$258.20
Purchase #5	$82.66	9.429%	$90.454	$90.45	$90.45	$90.50
Purchase #6	$84.28	13.772%	$95.887	$95.89	$95.90	$95.90
Purchase #7	$91.88	9.713%	$100.8043	$100.80	$100.80	$100.80
7 purchase totals =	$1,018.46		$1,091.5749	$1,091.57	$1,091.55	$1,091.70