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	$125.67	5.281%	$132.3066	$132.31	$132.30	$132.30
Purchase #2	$149.37	11.723%	$166.8806	$166.88	$166.90	$166.90
Purchase #3	$55.32	6.572%	$58.9556	$58.96	$58.95	$59.00
Purchase #4	$39.32	7.665%	$42.3339	$42.33	$42.35	$42.30
Purchase #5	$19.91	9.867%	$21.8745	$21.87	$21.85	$21.90
Purchase #6	$16.98	11.420%	$18.9191	$18.92	$18.90	$18.90
Purchase #7	$219.78	5.205%	$231.2195	$231.22	$231.20	$231.20
7 purchase totals =	$626.35		$672.4898	$672.49	$672.45	$672.50