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	$130.90	8.150%	$141.5684	$141.57	$141.55	$141.60
Purchase #2	$158.39	13.827%	$180.2906	$180.29	$180.30	$180.30
Purchase #3	$229.82	8.324%	$248.9502	$248.95	$248.95	$249.00
Purchase #4	$18.75	9.587%	$20.5476	$20.55	$20.55	$20.50
Purchase #5	$198.82	7.821%	$214.3697	$214.37	$214.35	$214.40
Purchase #6	$200.90	11.739%	$224.4837	$224.48	$224.50	$224.50
Purchase #7	$54.56	13.143%	$61.7308	$61.73	$61.75	$61.70
7 purchase totals =	$992.14		$1,091.9410	$1,091.94	$1,091.95	$1,092.00