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	$126.75	4.465%	$132.4094	$132.41	$132.40	$132.40
Purchase #2	$95.98	5.644%	$101.3971	$101.40	$101.40	$101.40
Purchase #3	$138.79	9.729%	$152.2929	$152.29	$152.30	$152.30
Purchase #4	$19.33	9.547%	$21.1754	$21.18	$21.20	$21.20
Purchase #5	$85.67	5.330%	$90.2362	$90.24	$90.25	$90.20
Purchase #6	$215.75	10.275%	$237.9183	$237.92	$237.90	$237.90
Purchase #7	$136.71	11.560%	$152.5137	$152.51	$152.50	$152.50
7 purchase totals =	$818.98		$887.9430	$887.95	$887.95	$887.90