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	$29.98	11.241%	$33.3501	$33.35	$33.35	$33.40
Purchase #2	$184.88	13.259%	$209.3932	$209.39	$209.40	$209.40
Purchase #3	$130.49	4.492%	$136.3516	$136.35	$136.35	$136.40
Purchase #4	$107.98	3.682%	$111.9558	$111.96	$111.95	$112.00
Purchase #5	$200.64	11.105%	$222.9211	$222.92	$222.90	$222.90
Purchase #6	$173.87	4.325%	$181.3899	$181.39	$181.40	$181.40
Purchase #7	$206.48	8.855%	$224.7638	$224.76	$224.75	$224.80
7 purchase totals =	$1,034.32		$1,120.1255	$1,120.12	$1,120.10	$1,120.30