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	$132.96	9.161%	$145.1405	$145.14	$145.15	$145.10
Purchase #2	$79.29	7.649%	$85.3549	$85.35	$85.35	$85.40
Purchase #3	$114.51	7.474%	$123.0685	$123.07	$123.05	$123.10
Purchase #4	$79.58	3.367%	$82.2595	$82.26	$82.25	$82.30
Purchase #5	$58.59	10.553%	$64.773	$64.77	$64.75	$64.80
Purchase #6	$225.54	8.241%	$244.1268	$244.13	$244.15	$244.10
Purchase #7	$146.88	10.459%	$162.2422	$162.24	$162.25	$162.20
7 purchase totals =	$837.35		$906.9654	$906.96	$906.95	$907.00