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	$178.32	7.574%	$191.826	$191.83	$191.85	$191.80
Purchase #2	$25.58	5.127%	$26.8915	$26.89	$26.90	$26.90
Purchase #3	$242.41	3.483%	$250.8531	$250.85	$250.85	$250.90
Purchase #4	$49.46	12.351%	$55.5688	$55.57	$55.55	$55.60
Purchase #5	$53.47	7.304%	$57.3754	$57.38	$57.40	$57.40
Purchase #6	$59.67	3.517%	$61.7686	$61.77	$61.75	$61.80
Purchase #7	$139.66	7.121%	$149.6052	$149.61	$149.60	$149.60
7 purchase totals =	$748.57		$793.8886	$793.90	$793.90	$794.00