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	$78.47	9.243%	$85.723	$85.72	$85.70	$85.70
Purchase #2	$31.40	9.627%	$34.4229	$34.42	$34.40	$34.40
Purchase #3	$200.56	10.406%	$221.4303	$221.43	$221.45	$221.40
Purchase #4	$83.29	6.150%	$88.4123	$88.41	$88.40	$88.40
Purchase #5	$110.28	9.219%	$120.4467	$120.45	$120.45	$120.40
Purchase #6	$93.75	6.185%	$99.5484	$99.55	$99.55	$99.50
Purchase #7	$202.42	10.511%	$223.6964	$223.70	$223.70	$223.70
7 purchase totals =	$800.17		$873.6800	$873.68	$873.65	$873.50