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	$78.85	8.733%	$85.736	$85.74	$85.75	$85.70
Purchase #2	$80.26	11.546%	$89.5268	$89.53	$89.55	$89.50
Purchase #3	$204.33	8.112%	$220.9052	$220.91	$220.90	$220.90
Purchase #4	$142.89	9.819%	$156.9204	$156.92	$156.90	$156.90
Purchase #5	$47.72	13.637%	$54.2276	$54.23	$54.25	$54.20
Purchase #6	$183.88	9.159%	$200.7216	$200.72	$200.70	$200.70
Purchase #7	$142.38	8.744%	$154.8297	$154.83	$154.85	$154.80
7 purchase totals =	$880.31		$962.8673	$962.88	$962.90	$962.70