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	$214.30	5.204%	$225.4522	$225.45	$225.45	$225.50
Purchase #2	$28.74	8.248%	$31.1105	$31.11	$31.10	$31.10
Purchase #3	$233.69	12.532%	$262.976	$262.98	$263.00	$263.00
Purchase #4	$145.87	11.597%	$162.7865	$162.79	$162.80	$162.80
Purchase #5	$31.88	5.674%	$33.6889	$33.69	$33.70	$33.70
Purchase #6	$40.45	3.592%	$41.903	$41.90	$41.90	$41.90
Purchase #7	$32.80	11.555%	$36.59	$36.59	$36.60	$36.60
7 purchase totals =	$727.73		$794.5071	$794.51	$794.55	$794.60