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	$139.73	3.251%	$144.2726	$144.27	$144.25	$144.30
Purchase #2	$123.53	6.527%	$131.5928	$131.59	$131.60	$131.60
Purchase #3	$178.74	5.767%	$189.0479	$189.05	$189.05	$189.00
Purchase #4	$241.41	6.125%	$256.1964	$256.20	$256.20	$256.20
Purchase #5	$104.53	11.121%	$116.1548	$116.15	$116.15	$116.20
Purchase #6	$50.94	6.563%	$54.2832	$54.28	$54.30	$54.30
Purchase #7	$144.87	11.467%	$161.4822	$161.48	$161.50	$161.50
7 purchase totals =	$983.75		$1,053.0299	$1,053.02	$1,053.05	$1,053.10