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	$35.94	6.797%	$38.3828	$38.38	$38.40	$38.40
Purchase #2	$11.84	8.182%	$12.8087	$12.81	$12.80	$12.80
Purchase #3	$22.97	6.178%	$24.3891	$24.39	$24.40	$24.40
Purchase #4	$59.56	5.478%	$62.8227	$62.82	$62.80	$62.80
Purchase #5	$24.89	10.642%	$27.5388	$27.54	$27.55	$27.50
Purchase #6	$216.86	6.574%	$231.1164	$231.12	$231.10	$231.10
Purchase #7	$84.27	9.711%	$92.4535	$92.45	$92.45	$92.50
7 purchase totals =	$456.33		$489.5120	$489.51	$489.50	$489.50