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	$202.49	13.443%	$229.7107	$229.71	$229.70	$229.70
Purchase #2	$222.93	11.481%	$248.5246	$248.52	$248.50	$248.50
Purchase #3	$168.63	11.632%	$188.245	$188.25	$188.25	$188.20
Purchase #4	$35.68	10.808%	$39.5363	$39.54	$39.55	$39.50
Purchase #5	$78.90	4.726%	$82.6288	$82.63	$82.65	$82.60
Purchase #6	$56.62	6.792%	$60.4656	$60.47	$60.45	$60.50
Purchase #7	$71.73	4.252%	$74.78	$74.78	$74.80	$74.80
7 purchase totals =	$836.98		$923.8910	$923.90	$923.90	$923.80