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	$94.49	11.394%	$105.2562	$105.26	$105.25	$105.30
Purchase #2	$71.52	10.227%	$78.8344	$78.83	$78.85	$78.80
Purchase #3	$175.97	9.776%	$193.1728	$193.17	$193.15	$193.20
Purchase #4	$202.82	10.113%	$223.3312	$223.33	$223.35	$223.30
Purchase #5	$84.86	7.588%	$91.2992	$91.30	$91.30	$91.30
Purchase #6	$33.67	12.439%	$37.8582	$37.86	$37.85	$37.90
Purchase #7	$229.52	5.695%	$242.5912	$242.59	$242.60	$242.60
7 purchase totals =	$892.85		$972.3432	$972.34	$972.35	$972.40