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	$146.99	13.719%	$167.1556	$167.16	$167.15	$167.20
Purchase #2	$223.29	8.582%	$242.4527	$242.45	$242.45	$242.50
Purchase #3	$64.62	11.443%	$72.0145	$72.01	$72.00	$72.00
Purchase #4	$215.80	6.560%	$229.9565	$229.96	$229.95	$230.00
Purchase #5	$142.66	5.167%	$150.0312	$150.03	$150.05	$150.00
Purchase #6	$97.90	9.178%	$106.8853	$106.89	$106.90	$106.90
Purchase #7	$75.69	8.369%	$82.0245	$82.02	$82.00	$82.00
7 purchase totals =	$966.95		$1,050.5203	$1,050.52	$1,050.50	$1,050.60