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	$52.69	8.430%	$57.1318	$57.13	$57.15	$57.10
Purchase #2	$42.68	5.599%	$45.0697	$45.07	$45.05	$45.10
Purchase #3	$141.83	5.792%	$150.0448	$150.04	$150.05	$150.00
Purchase #4	$173.35	7.109%	$185.6735	$185.67	$185.65	$185.70
Purchase #5	$181.79	5.553%	$191.8848	$191.88	$191.90	$191.90
Purchase #6	$191.76	4.579%	$200.5407	$200.54	$200.55	$200.50
Purchase #7	$223.76	9.422%	$244.8427	$244.84	$244.85	$244.80
7 purchase totals =	$1,007.86		$1,075.1880	$1,075.17	$1,075.20	$1,075.10