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	$61.86	13.562%	$70.2495	$70.25	$70.25	$70.20
Purchase #2	$111.44	7.322%	$119.5996	$119.60	$119.60	$119.60
Purchase #3	$10.70	13.460%	$12.1402	$12.14	$12.15	$12.10
Purchase #4	$57.46	3.786%	$59.6354	$59.64	$59.65	$59.60
Purchase #5	$137.33	5.756%	$145.2347	$145.23	$145.25	$145.20
Purchase #6	$54.36	12.471%	$61.1392	$61.14	$61.15	$61.10
Purchase #7	$131.87	10.869%	$146.203	$146.20	$146.20	$146.20
7 purchase totals =	$565.02		$614.2016	$614.20	$614.25	$614.00