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	$116.47	12.298%	$130.7935	$130.79	$130.80	$130.80
Purchase #2	$174.94	12.130%	$196.1602	$196.16	$196.15	$196.20
Purchase #3	$216.26	13.874%	$246.2639	$246.26	$246.25	$246.30
Purchase #4	$129.77	4.295%	$135.3436	$135.34	$135.35	$135.30
Purchase #5	$53.50	4.817%	$56.0771	$56.08	$56.10	$56.10
Purchase #6	$189.61	3.662%	$196.5535	$196.55	$196.55	$196.60
Purchase #7	$90.37	12.726%	$101.8705	$101.87	$101.85	$101.90
7 purchase totals =	$970.92		$1,063.0623	$1,063.05	$1,063.05	$1,063.20