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	$205.51	13.595%	$233.4491	$233.45	$233.45	$233.40
Purchase #2	$27.59	6.862%	$29.4832	$29.48	$29.50	$29.50
Purchase #3	$20.38	7.430%	$21.8942	$21.89	$21.90	$21.90
Purchase #4	$75.26	4.160%	$78.3908	$78.39	$78.40	$78.40
Purchase #5	$85.75	10.446%	$94.7074	$94.71	$94.70	$94.70
Purchase #6	$75.29	10.370%	$83.0976	$83.10	$83.10	$83.10
Purchase #7	$210.46	6.557%	$224.2599	$224.26	$224.25	$224.30
7 purchase totals =	$700.24		$765.2822	$765.28	$765.30	$765.30