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	$115.43	6.569%	$123.0126	$123.01	$123.00	$123.00
Purchase #2	$175.71	13.424%	$199.2973	$199.30	$199.30	$199.30
Purchase #3	$42.43	7.175%	$45.4744	$45.47	$45.45	$45.50
Purchase #4	$175.69	5.137%	$184.7152	$184.72	$184.70	$184.70
Purchase #5	$47.36	12.545%	$53.3013	$53.30	$53.30	$53.30
Purchase #6	$106.78	6.316%	$113.5242	$113.52	$113.50	$113.50
Purchase #7	$229.77	5.858%	$243.2299	$243.23	$243.25	$243.20
7 purchase totals =	$893.17		$962.5549	$962.55	$962.50	$962.50