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	$191.57	13.423%	$217.2844	$217.28	$217.30	$217.30
Purchase #2	$91.90	10.282%	$101.3492	$101.35	$101.35	$101.30
Purchase #3	$245.35	7.826%	$264.5511	$264.55	$264.55	$264.60
Purchase #4	$91.81	9.464%	$100.4989	$100.50	$100.50	$100.50
Purchase #5	$99.53	11.786%	$111.2606	$111.26	$111.25	$111.30
Purchase #6	$81.79	4.124%	$85.163	$85.16	$85.15	$85.20
Purchase #7	$104.32	9.350%	$114.0739	$114.07	$114.05	$114.10
7 purchase totals =	$906.27		$994.1811	$994.17	$994.15	$994.30