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	$82.98	7.699%	$89.3686	$89.37	$89.35	$89.40
Purchase #2	$88.78	3.163%	$91.5881	$91.59	$91.60	$91.60
Purchase #3	$25.58	4.397%	$26.7048	$26.70	$26.70	$26.70
Purchase #4	$90.98	11.292%	$101.2535	$101.25	$101.25	$101.30
Purchase #5	$134.28	12.781%	$151.4423	$151.44	$151.45	$151.40
Purchase #6	$99.91	12.543%	$112.4417	$112.44	$112.45	$112.40
Purchase #7	$231.41	5.154%	$243.3369	$243.34	$243.35	$243.30
7 purchase totals =	$753.92		$816.1359	$816.13	$816.15	$816.10