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	$208.78	11.375%	$232.5287	$232.53	$232.55	$232.50
Purchase #2	$15.30	3.224%	$15.7933	$15.79	$15.80	$15.80
Purchase #3	$60.91	11.839%	$68.1211	$68.12	$68.10	$68.10
Purchase #4	$139.55	4.727%	$146.1465	$146.15	$146.15	$146.10
Purchase #5	$199.47	3.191%	$205.8351	$205.84	$205.85	$205.80
Purchase #6	$78.65	13.786%	$89.4927	$89.49	$89.50	$89.50
Purchase #7	$221.97	12.849%	$250.4909	$250.49	$250.50	$250.50
7 purchase totals =	$924.63		$1,008.4083	$1,008.41	$1,008.45	$1,008.30