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	$240.48	4.352%	$250.9457	$250.95	$250.95	$250.90
Purchase #2	$150.37	7.478%	$161.6147	$161.61	$161.60	$161.60
Purchase #3	$161.71	5.643%	$170.8353	$170.84	$170.85	$170.80
Purchase #4	$124.92	5.520%	$131.8156	$131.82	$131.80	$131.80
Purchase #5	$196.76	6.591%	$209.7285	$209.73	$209.75	$209.70
Purchase #6	$47.87	5.350%	$50.431	$50.43	$50.45	$50.40
Purchase #7	$32.40	4.389%	$33.822	$33.82	$33.80	$33.80
7 purchase totals =	$954.51		$1,009.1928	$1,009.20	$1,009.20	$1,009.00