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	$199.85	3.510%	$206.8647	$206.86	$206.85	$206.90
Purchase #2	$197.35	13.320%	$223.637	$223.64	$223.65	$223.60
Purchase #3	$192.78	3.472%	$199.4733	$199.47	$199.45	$199.50
Purchase #4	$215.25	10.413%	$237.664	$237.66	$237.65	$237.70
Purchase #5	$127.88	10.376%	$141.1488	$141.15	$141.15	$141.10
Purchase #6	$28.72	11.793%	$32.1069	$32.11	$32.10	$32.10
Purchase #7	$81.49	6.153%	$86.5041	$86.50	$86.50	$86.50
7 purchase totals =	$1,043.32		$1,127.3988	$1,127.39	$1,127.35	$1,127.40