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	$147.61	7.415%	$158.5553	$158.56	$158.55	$158.60
Purchase #2	$227.48	9.388%	$248.8358	$248.84	$248.85	$248.80
Purchase #3	$111.92	4.500%	$116.9564	$116.96	$116.95	$117.00
Purchase #4	$124.25	6.145%	$131.8852	$131.89	$131.90	$131.90
Purchase #5	$180.84	7.850%	$195.0359	$195.04	$195.05	$195.00
Purchase #6	$85.40	13.436%	$96.8743	$96.87	$96.85	$96.90
Purchase #7	$48.33	4.129%	$50.3255	$50.33	$50.35	$50.30
7 purchase totals =	$925.83		$998.4684	$998.49	$998.50	$998.50