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	$146.89	3.627%	$152.2177	$152.22	$152.20	$152.20
Purchase #2	$30.34	7.139%	$32.506	$32.51	$32.50	$32.50
Purchase #3	$150.27	9.328%	$164.2872	$164.29	$164.30	$164.30
Purchase #4	$37.95	6.404%	$40.3803	$40.38	$40.40	$40.40
Purchase #5	$10.47	10.139%	$11.5316	$11.53	$11.55	$11.50
Purchase #6	$52.96	13.112%	$59.9041	$59.90	$59.90	$59.90
Purchase #7	$238.33	6.323%	$253.3996	$253.40	$253.40	$253.40
7 purchase totals =	$667.21		$714.2265	$714.23	$714.25	$714.20