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	$166.98	9.318%	$182.5392	$182.54	$182.55	$182.50
Purchase #2	$98.49	13.218%	$111.5084	$111.51	$111.50	$111.50
Purchase #3	$239.85	11.659%	$267.8141	$267.81	$267.80	$267.80
Purchase #4	$240.67	10.137%	$265.0667	$265.07	$265.05	$265.10
Purchase #5	$92.73	7.455%	$99.643	$99.64	$99.65	$99.60
Purchase #6	$99.42	5.205%	$104.5948	$104.59	$104.60	$104.60
Purchase #7	$180.29	9.239%	$196.947	$196.95	$196.95	$196.90
7 purchase totals =	$1,118.43		$1,228.1132	$1,228.11	$1,228.10	$1,228.00