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	$114.98	11.285%	$127.9555	$127.96	$127.95	$128.00
Purchase #2	$25.65	4.801%	$26.8815	$26.88	$26.90	$26.90
Purchase #3	$102.79	8.727%	$111.7605	$111.76	$111.75	$111.80
Purchase #4	$48.68	13.446%	$55.2255	$55.23	$55.25	$55.20
Purchase #5	$181.57	9.860%	$199.4728	$199.47	$199.45	$199.50
Purchase #6	$81.73	11.129%	$90.8257	$90.83	$90.85	$90.80
Purchase #7	$122.30	3.353%	$126.4007	$126.40	$126.40	$126.40
7 purchase totals =	$677.70		$738.5222	$738.53	$738.55	$738.60