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	$127.70	13.790%	$145.3098	$145.31	$145.30	$145.30
Purchase #2	$128.90	9.585%	$141.2551	$141.26	$141.25	$141.30
Purchase #3	$119.70	3.442%	$123.8201	$123.82	$123.80	$123.80
Purchase #4	$250.90	13.776%	$285.464	$285.46	$285.45	$285.50
Purchase #5	$29.68	6.340%	$31.5617	$31.56	$31.55	$31.60
Purchase #6	$106.95	3.796%	$111.0098	$111.01	$111.00	$111.00
Purchase #7	$188.76	3.370%	$195.1212	$195.12	$195.10	$195.10
7 purchase totals =	$952.59		$1,033.5417	$1,033.54	$1,033.45	$1,033.60