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	$237.52	4.575%	$248.3865	$248.39	$248.40	$248.40
Purchase #2	$250.51	6.444%	$266.6529	$266.65	$266.65	$266.70
Purchase #3	$44.42	3.121%	$45.8063	$45.81	$45.80	$45.80
Purchase #4	$171.86	4.464%	$179.5318	$179.53	$179.55	$179.50
Purchase #5	$99.96	11.838%	$111.7933	$111.79	$111.80	$111.80
Purchase #6	$21.61	4.834%	$22.6546	$22.65	$22.65	$22.70
Purchase #7	$138.54	4.674%	$145.0154	$145.02	$145.00	$145.00
7 purchase totals =	$964.42		$1,019.8408	$1,019.84	$1,019.85	$1,019.90