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	$164.38	10.848%	$182.2119	$182.21	$182.20	$182.20
Purchase #2	$123.30	10.567%	$136.3291	$136.33	$136.35	$136.30
Purchase #3	$30.87	3.603%	$31.9822	$31.98	$32.00	$32.00
Purchase #4	$85.73	11.385%	$95.4904	$95.49	$95.50	$95.50
Purchase #5	$17.70	11.694%	$19.7698	$19.77	$19.75	$19.80
Purchase #6	$221.61	3.577%	$229.537	$229.54	$229.55	$229.50
Purchase #7	$41.38	10.800%	$45.849	$45.85	$45.85	$45.80
7 purchase totals =	$684.97		$741.1694	$741.17	$741.20	$741.10