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	$36.78	12.681%	$41.4441	$41.44	$41.45	$41.40
Purchase #2	$107.43	6.589%	$114.5086	$114.51	$114.50	$114.50
Purchase #3	$130.84	9.391%	$143.1272	$143.13	$143.15	$143.10
Purchase #4	$125.54	4.606%	$131.3224	$131.32	$131.30	$131.30
Purchase #5	$172.58	7.559%	$185.6253	$185.63	$185.65	$185.60
Purchase #6	$207.97	11.126%	$231.1087	$231.11	$231.10	$231.10
Purchase #7	$238.41	13.618%	$270.8767	$270.88	$270.90	$270.90
7 purchase totals =	$1,019.55		$1,118.0130	$1,118.02	$1,118.05	$1,117.90