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	$167.39	11.382%	$186.4423	$186.44	$186.45	$186.40
Purchase #2	$48.69	13.640%	$55.3313	$55.33	$55.35	$55.30
Purchase #3	$97.34	9.140%	$106.2369	$106.24	$106.25	$106.20
Purchase #4	$128.28	6.720%	$136.9004	$136.90	$136.90	$136.90
Purchase #5	$81.35	11.208%	$90.4677	$90.47	$90.45	$90.50
Purchase #6	$124.69	10.213%	$137.4246	$137.42	$137.40	$137.40
Purchase #7	$198.28	7.602%	$213.3532	$213.35	$213.35	$213.40
7 purchase totals =	$846.02		$926.1564	$926.15	$926.15	$926.10