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	$103.79	12.356%	$116.6143	$116.61	$116.60	$116.60
Purchase #2	$143.30	12.445%	$161.1337	$161.13	$161.15	$161.10
Purchase #3	$229.60	5.446%	$242.104	$242.10	$242.10	$242.10
Purchase #4	$248.94	4.488%	$260.1124	$260.11	$260.10	$260.10
Purchase #5	$40.70	4.620%	$42.5803	$42.58	$42.60	$42.60
Purchase #6	$60.63	7.439%	$65.1403	$65.14	$65.15	$65.10
Purchase #7	$147.86	7.656%	$159.1802	$159.18	$159.20	$159.20
7 purchase totals =	$974.82		$1,046.8652	$1,046.85	$1,046.90	$1,046.80