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	$93.88	6.665%	$100.1371	$100.14	$100.15	$100.10
Purchase #2	$96.53	4.789%	$101.1528	$101.15	$101.15	$101.20
Purchase #3	$117.88	12.246%	$132.3156	$132.32	$132.30	$132.30
Purchase #4	$147.85	3.409%	$152.8902	$152.89	$152.90	$152.90
Purchase #5	$22.76	9.447%	$24.9101	$24.91	$24.90	$24.90
Purchase #6	$119.76	9.714%	$131.3935	$131.39	$131.40	$131.40
Purchase #7	$9.35	8.686%	$10.1621	$10.16	$10.15	$10.20
7 purchase totals =	$608.01		$652.9614	$652.96	$652.95	$653.00