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	$191.76	10.272%	$211.4576	$211.46	$211.45	$211.50
Purchase #2	$133.77	13.448%	$151.7594	$151.76	$151.75	$151.80
Purchase #3	$53.78	11.430%	$59.9271	$59.93	$59.95	$59.90
Purchase #4	$39.94	13.735%	$45.4258	$45.43	$45.45	$45.40
Purchase #5	$183.74	4.102%	$191.277	$191.28	$191.30	$191.30
Purchase #6	$150.84	3.344%	$155.8841	$155.88	$155.90	$155.90
Purchase #7	$83.39	7.775%	$89.8736	$89.87	$89.85	$89.90
7 purchase totals =	$837.22		$905.6046	$905.61	$905.65	$905.70