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	$22.85	7.234%	$24.503	$24.50	$24.50	$24.50
Purchase #2	$141.41	10.442%	$156.176	$156.18	$156.20	$156.20
Purchase #3	$25.53	11.693%	$28.5152	$28.52	$28.50	$28.50
Purchase #4	$39.78	12.566%	$44.7788	$44.78	$44.80	$44.80
Purchase #5	$78.61	3.444%	$81.3173	$81.32	$81.30	$81.30
Purchase #6	$244.35	7.339%	$262.2828	$262.28	$262.30	$262.30
Purchase #7	$149.71	10.113%	$164.8502	$164.85	$164.85	$164.90
7 purchase totals =	$702.24		$762.4233	$762.43	$762.45	$762.50