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	$148.42	7.114%	$158.9786	$158.98	$159.00	$159.00
Purchase #2	$88.51	13.382%	$100.3544	$100.35	$100.35	$100.40
Purchase #3	$90.74	8.270%	$98.2442	$98.24	$98.25	$98.20
Purchase #4	$42.33	11.743%	$47.3008	$47.30	$47.30	$47.30
Purchase #5	$179.86	10.613%	$198.9485	$198.95	$198.95	$198.90
Purchase #6	$88.81	10.362%	$98.0125	$98.01	$98.00	$98.00
Purchase #7	$223.29	13.519%	$253.4766	$253.48	$253.50	$253.50
7 purchase totals =	$861.96		$955.3156	$955.31	$955.35	$955.30