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	$249.50	13.247%	$282.5513	$282.55	$282.55	$282.60
Purchase #2	$32.93	13.677%	$37.4338	$37.43	$37.45	$37.40
Purchase #3	$55.78	4.325%	$58.1925	$58.19	$58.20	$58.20
Purchase #4	$246.30	11.445%	$274.489	$274.49	$274.50	$274.50
Purchase #5	$39.67	4.536%	$41.4694	$41.47	$41.45	$41.50
Purchase #6	$123.91	13.474%	$140.6056	$140.61	$140.60	$140.60
Purchase #7	$191.38	4.271%	$199.5538	$199.55	$199.55	$199.60
7 purchase totals =	$939.47		$1,034.2954	$1,034.29	$1,034.30	$1,034.40