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	$204.41	10.337%	$225.5399	$225.54	$225.55	$225.50
Purchase #2	$109.28	7.297%	$117.2542	$117.25	$117.25	$117.30
Purchase #3	$86.53	3.245%	$89.3379	$89.34	$89.35	$89.30
Purchase #4	$117.34	9.230%	$128.1705	$128.17	$128.15	$128.20
Purchase #5	$29.26	9.547%	$32.0535	$32.05	$32.05	$32.10
Purchase #6	$37.74	3.743%	$39.1526	$39.15	$39.15	$39.20
Purchase #7	$188.80	4.212%	$196.7523	$196.75	$196.75	$196.80
7 purchase totals =	$773.36		$828.2609	$828.25	$828.25	$828.40