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	$62.67	13.751%	$71.2878	$71.29	$71.30	$71.30
Purchase #2	$150.37	10.309%	$165.8716	$165.87	$165.85	$165.90
Purchase #3	$149.65	8.458%	$162.3074	$162.31	$162.30	$162.30
Purchase #4	$74.84	12.171%	$83.9488	$83.95	$83.95	$83.90
Purchase #5	$191.67	4.706%	$200.69	$200.69	$200.70	$200.70
Purchase #6	$102.77	12.190%	$115.2977	$115.30	$115.30	$115.30
Purchase #7	$64.74	11.713%	$72.323	$72.32	$72.30	$72.30
7 purchase totals =	$796.71		$871.7263	$871.73	$871.70	$871.70