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	$187.82	12.262%	$210.8505	$210.85	$210.85	$210.90
Purchase #2	$225.61	5.280%	$237.5222	$237.52	$237.50	$237.50
Purchase #3	$104.93	5.513%	$110.7148	$110.71	$110.70	$110.70
Purchase #4	$108.81	10.701%	$120.4538	$120.45	$120.45	$120.50
Purchase #5	$31.41	7.562%	$33.7852	$33.79	$33.80	$33.80
Purchase #6	$127.29	12.700%	$143.4558	$143.46	$143.45	$143.50
Purchase #7	$229.67	13.126%	$259.8165	$259.82	$259.80	$259.80
7 purchase totals =	$1,015.54		$1,116.5988	$1,116.60	$1,116.55	$1,116.70