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	$150.61	5.276%	$158.5562	$158.56	$158.55	$158.60
Purchase #2	$162.26	11.511%	$180.9377	$180.94	$180.95	$180.90
Purchase #3	$115.74	12.657%	$130.3892	$130.39	$130.40	$130.40
Purchase #4	$107.79	5.123%	$113.3121	$113.31	$113.30	$113.30
Purchase #5	$62.78	7.530%	$67.5073	$67.51	$67.50	$67.50
Purchase #6	$237.27	7.174%	$254.2917	$254.29	$254.30	$254.30
Purchase #7	$140.42	11.692%	$156.8379	$156.84	$156.85	$156.80
7 purchase totals =	$976.87		$1,061.8321	$1,061.84	$1,061.85	$1,061.80