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	$197.50	12.246%	$221.6859	$221.69	$221.70	$221.70
Purchase #2	$115.54	9.123%	$126.0807	$126.08	$126.10	$126.10
Purchase #3	$229.86	4.460%	$240.1118	$240.11	$240.10	$240.10
Purchase #4	$50.56	5.309%	$53.2442	$53.24	$53.25	$53.20
Purchase #5	$106.72	4.558%	$111.5843	$111.58	$111.60	$111.60
Purchase #6	$217.79	3.813%	$226.0943	$226.09	$226.10	$226.10
Purchase #7	$29.90	12.567%	$33.6575	$33.66	$33.65	$33.70
7 purchase totals =	$947.87		$1,012.4587	$1,012.45	$1,012.50	$1,012.50