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	$227.63	5.764%	$240.7506	$240.75	$240.75	$240.80
Purchase #2	$88.71	11.569%	$98.9729	$98.97	$98.95	$99.00
Purchase #3	$11.45	9.484%	$12.5359	$12.54	$12.55	$12.50
Purchase #4	$26.68	4.315%	$27.8312	$27.83	$27.85	$27.80
Purchase #5	$194.54	13.601%	$220.9994	$221.00	$221.00	$221.00
Purchase #6	$65.78	9.594%	$72.0909	$72.09	$72.10	$72.10
Purchase #7	$90.96	10.464%	$100.4781	$100.48	$100.50	$100.50
7 purchase totals =	$705.75		$773.6590	$773.66	$773.70	$773.70