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	$54.29	12.732%	$61.2022	$61.20	$61.20	$61.20
Purchase #2	$124.38	6.160%	$132.0418	$132.04	$132.05	$132.00
Purchase #3	$136.45	9.422%	$149.3063	$149.31	$149.30	$149.30
Purchase #4	$237.64	11.321%	$264.5432	$264.54	$264.55	$264.50
Purchase #5	$113.79	4.685%	$119.1211	$119.12	$119.10	$119.10
Purchase #6	$152.48	10.230%	$168.0787	$168.08	$168.10	$168.10
Purchase #7	$38.58	11.826%	$43.1425	$43.14	$43.15	$43.10
7 purchase totals =	$857.61		$937.4358	$937.43	$937.45	$937.30