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	$207.92	12.169%	$233.2218	$233.22	$233.20	$233.20
Purchase #2	$169.73	7.533%	$182.5158	$182.52	$182.50	$182.50
Purchase #3	$42.99	6.104%	$45.6141	$45.61	$45.60	$45.60
Purchase #4	$57.84	3.464%	$59.8436	$59.84	$59.85	$59.80
Purchase #5	$84.59	13.188%	$95.7457	$95.75	$95.75	$95.70
Purchase #6	$95.68	3.107%	$98.6528	$98.65	$98.65	$98.70
Purchase #7	$201.31	4.180%	$209.7248	$209.72	$209.70	$209.70
7 purchase totals =	$860.06		$925.3186	$925.31	$925.25	$925.20