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	$94.58	5.346%	$99.6362	$99.64	$99.65	$99.60
Purchase #2	$243.96	4.579%	$255.1309	$255.13	$255.15	$255.10
Purchase #3	$85.73	13.534%	$97.3327	$97.33	$97.35	$97.30
Purchase #4	$187.75	4.157%	$195.5548	$195.55	$195.55	$195.60
Purchase #5	$152.29	9.409%	$166.619	$166.62	$166.60	$166.60
Purchase #6	$28.35	11.255%	$31.5408	$31.54	$31.55	$31.50
Purchase #7	$25.96	13.638%	$29.5004	$29.50	$29.50	$29.50
7 purchase totals =	$818.62		$875.3148	$875.31	$875.35	$875.20