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	$212.50	4.627%	$222.3324	$222.33	$222.35	$222.30
Purchase #2	$52.97	5.133%	$55.689	$55.69	$55.70	$55.70
Purchase #3	$158.74	11.511%	$177.0126	$177.01	$177.00	$177.00
Purchase #4	$85.69	5.598%	$90.4869	$90.49	$90.50	$90.50
Purchase #5	$61.89	13.735%	$70.3906	$70.39	$70.40	$70.40
Purchase #6	$33.58	9.174%	$36.6606	$36.66	$36.65	$36.70
Purchase #7	$55.51	7.391%	$59.6127	$59.61	$59.60	$59.60
7 purchase totals =	$660.88		$712.1848	$712.18	$712.20	$712.20