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	$130.78	10.481%	$144.4871	$144.49	$144.50	$144.50
Purchase #2	$141.96	12.195%	$159.272	$159.27	$159.25	$159.30
Purchase #3	$95.59	6.423%	$101.7297	$101.73	$101.75	$101.70
Purchase #4	$169.43	7.180%	$181.5951	$181.60	$181.60	$181.60
Purchase #5	$68.46	3.695%	$70.9896	$70.99	$71.00	$71.00
Purchase #6	$37.77	7.411%	$40.5691	$40.57	$40.55	$40.60
Purchase #7	$25.73	10.660%	$28.4728	$28.47	$28.45	$28.50
7 purchase totals =	$669.72		$727.1154	$727.12	$727.10	$727.20