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	$66.89	10.667%	$74.0252	$74.03	$74.05	$74.00
Purchase #2	$214.37	5.627%	$226.4326	$226.43	$226.45	$226.40
Purchase #3	$182.51	3.495%	$188.8887	$188.89	$188.90	$188.90
Purchase #4	$86.65	11.815%	$96.8877	$96.89	$96.90	$96.90
Purchase #5	$86.94	5.723%	$91.9156	$91.92	$91.90	$91.90
Purchase #6	$6.82	8.850%	$7.4236	$7.42	$7.40	$7.40
Purchase #7	$209.49	9.496%	$229.3832	$229.38	$229.40	$229.40
7 purchase totals =	$853.67		$914.9566	$914.96	$915.00	$914.90