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	$230.31	3.740%	$238.9236	$238.92	$238.90	$238.90
Purchase #2	$237.80	11.642%	$265.4847	$265.48	$265.50	$265.50
Purchase #3	$161.28	9.626%	$176.8048	$176.80	$176.80	$176.80
Purchase #4	$185.32	11.406%	$206.4576	$206.46	$206.45	$206.50
Purchase #5	$31.32	3.729%	$32.4879	$32.49	$32.50	$32.50
Purchase #6	$216.86	4.177%	$225.9182	$225.92	$225.90	$225.90
Purchase #7	$141.77	8.814%	$154.2656	$154.27	$154.25	$154.30
7 purchase totals =	$1,204.66		$1,300.3424	$1,300.34	$1,300.30	$1,300.40