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	$65.73	13.320%	$74.4852	$74.49	$74.50	$74.50
Purchase #2	$157.35	4.430%	$164.3206	$164.32	$164.30	$164.30
Purchase #3	$234.35	13.353%	$265.6428	$265.64	$265.65	$265.60
Purchase #4	$100.90	9.478%	$110.4633	$110.46	$110.45	$110.50
Purchase #5	$18.94	9.161%	$20.6751	$20.68	$20.70	$20.70
Purchase #6	$223.70	6.588%	$238.4374	$238.44	$238.45	$238.40
Purchase #7	$160.60	6.761%	$171.4582	$171.46	$171.45	$171.50
7 purchase totals =	$961.57		$1,045.4826	$1,045.49	$1,045.50	$1,045.50