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	$231.27	9.625%	$253.5297	$253.53	$253.55	$253.50
Purchase #2	$206.56	4.728%	$216.3262	$216.33	$216.35	$216.30
Purchase #3	$169.98	12.459%	$191.1578	$191.16	$191.15	$191.20
Purchase #4	$98.25	7.388%	$105.5087	$105.51	$105.50	$105.50
Purchase #5	$52.36	9.175%	$57.164	$57.16	$57.15	$57.20
Purchase #6	$38.76	9.577%	$42.472	$42.47	$42.45	$42.50
Purchase #7	$90.41	7.515%	$97.2043	$97.20	$97.20	$97.20
7 purchase totals =	$887.59		$963.3627	$963.36	$963.35	$963.40