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	$148.82	6.365%	$158.2924	$158.29	$158.30	$158.30
Purchase #2	$28.35	9.425%	$31.022	$31.02	$31.00	$31.00
Purchase #3	$151.46	4.555%	$158.359	$158.36	$158.35	$158.40
Purchase #4	$172.43	9.394%	$188.6281	$188.63	$188.65	$188.60
Purchase #5	$100.82	9.259%	$110.1549	$110.15	$110.15	$110.20
Purchase #6	$246.81	8.424%	$267.6013	$267.60	$267.60	$267.60
Purchase #7	$147.90	7.806%	$159.4451	$159.45	$159.45	$159.40
7 purchase totals =	$996.59		$1,073.5028	$1,073.50	$1,073.50	$1,073.50