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	$125.74	6.273%	$133.6277	$133.63	$133.65	$133.60
Purchase #2	$237.99	10.676%	$263.3978	$263.40	$263.40	$263.40
Purchase #3	$172.42	13.677%	$196.0019	$196.00	$196.00	$196.00
Purchase #4	$78.88	4.638%	$82.5385	$82.54	$82.55	$82.50
Purchase #5	$38.85	3.351%	$40.1519	$40.15	$40.15	$40.20
Purchase #6	$99.58	6.346%	$105.8993	$105.90	$105.90	$105.90
Purchase #7	$96.83	8.152%	$104.7236	$104.72	$104.70	$104.70
7 purchase totals =	$850.29		$926.3407	$926.34	$926.35	$926.30