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	$146.55	3.262%	$151.3305	$151.33	$151.35	$151.30
Purchase #2	$13.93	9.105%	$15.1983	$15.20	$15.20	$15.20
Purchase #3	$91.27	9.588%	$100.021	$100.02	$100.00	$100.00
Purchase #4	$28.64	9.231%	$31.2838	$31.28	$31.30	$31.30
Purchase #5	$96.60	13.157%	$109.3097	$109.31	$109.30	$109.30
Purchase #6	$226.76	7.134%	$242.9371	$242.94	$242.95	$242.90
Purchase #7	$116.54	11.433%	$129.864	$129.86	$129.85	$129.90
7 purchase totals =	$720.29		$779.9444	$779.94	$779.95	$779.90