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	$242.76	7.565%	$261.1248	$261.12	$261.10	$261.10
Purchase #2	$166.64	8.153%	$180.2262	$180.23	$180.25	$180.20
Purchase #3	$103.25	7.551%	$111.0464	$111.05	$111.05	$111.00
Purchase #4	$62.67	7.683%	$67.4849	$67.48	$67.50	$67.50
Purchase #5	$38.54	13.747%	$43.8381	$43.84	$43.85	$43.80
Purchase #6	$227.27	8.533%	$246.6629	$246.66	$246.65	$246.70
Purchase #7	$150.25	13.764%	$170.9304	$170.93	$170.95	$170.90
7 purchase totals =	$991.38		$1,081.3137	$1,081.31	$1,081.35	$1,081.20