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	$245.86	9.255%	$268.6143	$268.61	$268.60	$268.60
Purchase #2	$144.25	3.711%	$149.6031	$149.60	$149.60	$149.60
Purchase #3	$31.43	7.716%	$33.8551	$33.86	$33.85	$33.90
Purchase #4	$230.78	7.362%	$247.77	$247.77	$247.75	$247.80
Purchase #5	$30.36	8.615%	$32.9755	$32.98	$33.00	$33.00
Purchase #6	$227.42	4.256%	$237.099	$237.10	$237.10	$237.10
Purchase #7	$38.43	11.124%	$42.705	$42.71	$42.70	$42.70
7 purchase totals =	$948.53		$1,012.6220	$1,012.63	$1,012.60	$1,012.70