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	$85.39	4.841%	$89.5237	$89.52	$89.50	$89.50
Purchase #2	$94.95	11.319%	$105.6974	$105.70	$105.70	$105.70
Purchase #3	$61.69	6.720%	$65.8356	$65.84	$65.85	$65.80
Purchase #4	$66.31	13.538%	$75.287	$75.29	$75.30	$75.30
Purchase #5	$201.34	13.614%	$228.7504	$228.75	$228.75	$228.80
Purchase #6	$235.83	13.229%	$267.028	$267.03	$267.05	$267.00
Purchase #7	$59.39	3.438%	$61.4318	$61.43	$61.45	$61.40
7 purchase totals =	$804.90		$893.5539	$893.56	$893.60	$893.50