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	$179.25	3.734%	$185.9432	$185.94	$185.95	$185.90
Purchase #2	$105.27	10.564%	$116.3907	$116.39	$116.40	$116.40
Purchase #3	$121.45	7.529%	$130.594	$130.59	$130.60	$130.60
Purchase #4	$90.27	5.217%	$94.9794	$94.98	$95.00	$95.00
Purchase #5	$181.92	12.282%	$204.2634	$204.26	$204.25	$204.30
Purchase #6	$46.51	5.675%	$49.1494	$49.15	$49.15	$49.10
Purchase #7	$198.80	12.208%	$223.0695	$223.07	$223.05	$223.10
7 purchase totals =	$923.47		$1,004.3896	$1,004.38	$1,004.40	$1,004.40