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	$199.95	11.194%	$222.3324	$222.33	$222.35	$222.30
Purchase #2	$37.41	13.193%	$42.3455	$42.35	$42.35	$42.30
Purchase #3	$85.41	4.353%	$89.1279	$89.13	$89.15	$89.10
Purchase #4	$101.45	6.729%	$108.2766	$108.28	$108.30	$108.30
Purchase #5	$85.34	7.732%	$91.9385	$91.94	$91.95	$91.90
Purchase #6	$55.88	9.558%	$61.221	$61.22	$61.20	$61.20
Purchase #7	$128.87	8.328%	$139.6023	$139.60	$139.60	$139.60
7 purchase totals =	$694.31		$754.8442	$754.85	$754.90	$754.70