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	$150.89	9.634%	$165.4267	$165.43	$165.45	$165.40
Purchase #2	$172.93	5.441%	$182.3391	$182.34	$182.35	$182.30
Purchase #3	$123.30	4.520%	$128.8732	$128.87	$128.85	$128.90
Purchase #4	$98.80	6.736%	$105.4552	$105.46	$105.45	$105.50
Purchase #5	$239.31	7.254%	$256.6695	$256.67	$256.65	$256.70
Purchase #6	$153.33	13.453%	$173.9575	$173.96	$173.95	$174.00
Purchase #7	$83.26	5.849%	$88.1299	$88.13	$88.15	$88.10
7 purchase totals =	$1,021.82		$1,100.8511	$1,100.86	$1,100.85	$1,100.90