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	$186.72	7.411%	$200.5578	$200.56	$200.55	$200.60
Purchase #2	$21.86	12.159%	$24.518	$24.52	$24.50	$24.50
Purchase #3	$195.91	6.553%	$208.748	$208.75	$208.75	$208.70
Purchase #4	$29.59	9.157%	$32.2996	$32.30	$32.30	$32.30
Purchase #5	$150.40	9.806%	$165.1482	$165.15	$165.15	$165.10
Purchase #6	$91.95	8.458%	$99.7271	$99.73	$99.75	$99.70
Purchase #7	$76.93	8.505%	$83.4729	$83.47	$83.45	$83.50
7 purchase totals =	$753.36		$814.4716	$814.48	$814.45	$814.40