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	$196.86	13.540%	$223.5148	$223.51	$223.50	$223.50
Purchase #2	$85.28	9.295%	$93.2068	$93.21	$93.20	$93.20
Purchase #3	$195.65	13.332%	$221.7341	$221.73	$221.75	$221.70
Purchase #4	$91.52	4.525%	$95.6613	$95.66	$95.65	$95.70
Purchase #5	$86.28	3.812%	$89.569	$89.57	$89.55	$89.60
Purchase #6	$42.48	3.199%	$43.8389	$43.84	$43.85	$43.80
Purchase #7	$110.35	13.586%	$125.3422	$125.34	$125.35	$125.30
7 purchase totals =	$808.42		$892.8671	$892.86	$892.85	$892.80