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	$61.91	9.254%	$67.6392	$67.64	$67.65	$67.60
Purchase #2	$37.58	6.257%	$39.9314	$39.93	$39.95	$39.90
Purchase #3	$69.62	4.476%	$72.7362	$72.74	$72.75	$72.70
Purchase #4	$10.39	13.736%	$11.8172	$11.82	$11.80	$11.80
Purchase #5	$160.29	7.705%	$172.6403	$172.64	$172.65	$172.60
Purchase #6	$119.81	3.287%	$123.7482	$123.75	$123.75	$123.70
Purchase #7	$245.72	4.362%	$256.4383	$256.44	$256.45	$256.40
7 purchase totals =	$705.32		$744.9508	$744.96	$745.00	$744.70