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	$76.35	13.648%	$86.7702	$86.77	$86.75	$86.80
Purchase #2	$75.78	7.478%	$81.4468	$81.45	$81.45	$81.40
Purchase #3	$169.42	4.171%	$176.4865	$176.49	$176.50	$176.50
Purchase #4	$81.66	10.559%	$90.2825	$90.28	$90.30	$90.30
Purchase #5	$207.53	4.121%	$216.0823	$216.08	$216.10	$216.10
Purchase #6	$84.37	7.160%	$90.4109	$90.41	$90.40	$90.40
Purchase #7	$249.81	8.537%	$271.1363	$271.14	$271.15	$271.10
7 purchase totals =	$944.92		$1,012.6155	$1,012.62	$1,012.65	$1,012.60