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	$141.49	13.871%	$161.1161	$161.12	$161.10	$161.10
Purchase #2	$196.88	10.677%	$217.9009	$217.90	$217.90	$217.90
Purchase #3	$50.73	6.684%	$54.1208	$54.12	$54.10	$54.10
Purchase #4	$67.28	7.446%	$72.2897	$72.29	$72.30	$72.30
Purchase #5	$158.36	6.483%	$168.6265	$168.63	$168.65	$168.60
Purchase #6	$73.39	5.427%	$77.3729	$77.37	$77.35	$77.40
Purchase #7	$127.53	3.208%	$131.6212	$131.62	$131.60	$131.60
7 purchase totals =	$815.66		$883.0481	$883.05	$883.00	$883.00