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	$175.69	5.248%	$184.9102	$184.91	$184.90	$184.90
Purchase #2	$150.40	13.193%	$170.2423	$170.24	$170.25	$170.20
Purchase #3	$76.94	5.810%	$81.4102	$81.41	$81.40	$81.40
Purchase #4	$206.88	11.662%	$231.0063	$231.01	$231.00	$231.00
Purchase #5	$11.95	8.593%	$12.9769	$12.98	$13.00	$13.00
Purchase #6	$53.76	5.180%	$56.5448	$56.54	$56.55	$56.50
Purchase #7	$250.95	11.740%	$280.4115	$280.41	$280.40	$280.40
7 purchase totals =	$926.57		$1,017.5022	$1,017.50	$1,017.50	$1,017.40