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	$200.82	11.263%	$223.4384	$223.44	$223.45	$223.40
Purchase #2	$204.66	12.550%	$230.3448	$230.34	$230.35	$230.30
Purchase #3	$84.50	9.216%	$92.2875	$92.29	$92.30	$92.30
Purchase #4	$8.85	7.451%	$9.5094	$9.51	$9.50	$9.50
Purchase #5	$214.31	13.322%	$242.8604	$242.86	$242.85	$242.90
Purchase #6	$34.83	7.845%	$37.5624	$37.56	$37.55	$37.60
Purchase #7	$70.45	11.339%	$78.4383	$78.44	$78.45	$78.40
7 purchase totals =	$818.42		$914.4412	$914.44	$914.45	$914.40