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	$75.74	3.733%	$78.5674	$78.57	$78.55	$78.60
Purchase #2	$130.87	4.860%	$137.2303	$137.23	$137.25	$137.20
Purchase #3	$162.49	12.290%	$182.46	$182.46	$182.45	$182.50
Purchase #4	$108.59	9.515%	$118.9223	$118.92	$118.90	$118.90
Purchase #5	$250.56	4.142%	$260.9382	$260.94	$260.95	$260.90
Purchase #6	$39.65	3.468%	$41.0251	$41.03	$41.05	$41.00
Purchase #7	$225.27	11.181%	$250.4574	$250.46	$250.45	$250.50
7 purchase totals =	$993.17		$1,069.6007	$1,069.61	$1,069.60	$1,069.60