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	$76.45	12.671%	$86.137	$86.14	$86.15	$86.10
Purchase #2	$9.42	12.842%	$10.6297	$10.63	$10.65	$10.60
Purchase #3	$229.51	3.229%	$236.9209	$236.92	$236.90	$236.90
Purchase #4	$137.91	4.664%	$144.3421	$144.34	$144.35	$144.30
Purchase #5	$151.69	13.739%	$172.5307	$172.53	$172.55	$172.50
Purchase #6	$64.64	11.531%	$72.0936	$72.09	$72.10	$72.10
Purchase #7	$101.33	4.645%	$106.0368	$106.04	$106.05	$106.00
7 purchase totals =	$770.95		$828.6908	$828.69	$828.75	$828.50