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	$168.49	10.182%	$185.6457	$185.65	$185.65	$185.60
Purchase #2	$104.67	11.439%	$116.6432	$116.64	$116.65	$116.60
Purchase #3	$78.69	4.492%	$82.2248	$82.22	$82.20	$82.20
Purchase #4	$81.43	6.240%	$86.5112	$86.51	$86.50	$86.50
Purchase #5	$20.72	6.267%	$22.0185	$22.02	$22.00	$22.00
Purchase #6	$55.70	12.260%	$62.5288	$62.53	$62.55	$62.50
Purchase #7	$104.33	5.450%	$110.016	$110.02	$110.00	$110.00
7 purchase totals =	$614.03		$665.5882	$665.59	$665.55	$665.40