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	$209.37	10.336%	$231.0105	$231.01	$231.00	$231.00
Purchase #2	$123.98	11.248%	$137.9253	$137.93	$137.95	$137.90
Purchase #3	$56.72	7.864%	$61.1805	$61.18	$61.20	$61.20
Purchase #4	$140.96	12.326%	$158.3347	$158.33	$158.35	$158.30
Purchase #5	$115.98	8.779%	$126.1619	$126.16	$126.15	$126.20
Purchase #6	$94.97	4.658%	$99.3937	$99.39	$99.40	$99.40
Purchase #7	$146.77	4.148%	$152.858	$152.86	$152.85	$152.90
7 purchase totals =	$888.75		$966.8646	$966.86	$966.90	$966.90