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	$234.51	9.228%	$256.1506	$256.15	$256.15	$256.20
Purchase #2	$39.55	13.178%	$44.7619	$44.76	$44.75	$44.80
Purchase #3	$114.63	4.277%	$119.5327	$119.53	$119.55	$119.50
Purchase #4	$240.93	4.240%	$251.1454	$251.15	$251.15	$251.10
Purchase #5	$237.27	7.802%	$255.7818	$255.78	$255.80	$255.80
Purchase #6	$99.34	8.424%	$107.7084	$107.71	$107.70	$107.70
Purchase #7	$99.66	10.107%	$109.7326	$109.73	$109.75	$109.70
7 purchase totals =	$1,065.89		$1,144.8134	$1,144.81	$1,144.85	$1,144.80