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	$117.89	4.353%	$123.0218	$123.02	$123.00	$123.00
Purchase #2	$79.31	13.668%	$90.1501	$90.15	$90.15	$90.20
Purchase #3	$206.65	11.168%	$229.7287	$229.73	$229.75	$229.70
Purchase #4	$179.86	6.669%	$191.8549	$191.85	$191.85	$191.90
Purchase #5	$178.27	6.598%	$190.0323	$190.03	$190.05	$190.00
Purchase #6	$29.66	5.419%	$31.2673	$31.27	$31.25	$31.30
Purchase #7	$143.92	4.742%	$150.7447	$150.74	$150.75	$150.70
7 purchase totals =	$935.56		$1,006.7998	$1,006.79	$1,006.80	$1,006.80