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	$165.66	3.871%	$172.0727	$172.07	$172.05	$172.10
Purchase #2	$238.82	9.385%	$261.2333	$261.23	$261.25	$261.20
Purchase #3	$134.26	13.266%	$152.0709	$152.07	$152.05	$152.10
Purchase #4	$205.51	5.551%	$216.9179	$216.92	$216.90	$216.90
Purchase #5	$120.84	9.192%	$131.9476	$131.95	$131.95	$131.90
Purchase #6	$184.27	3.285%	$190.3233	$190.32	$190.30	$190.30
Purchase #7	$45.37	12.873%	$51.2105	$51.21	$51.20	$51.20
7 purchase totals =	$1,094.73		$1,175.7762	$1,175.77	$1,175.70	$1,175.70