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	$62.85	13.848%	$71.5535	$71.55	$71.55	$71.60
Purchase #2	$26.94	9.111%	$29.3945	$29.39	$29.40	$29.40
Purchase #3	$222.68	6.586%	$237.3457	$237.35	$237.35	$237.30
Purchase #4	$43.83	6.391%	$46.6312	$46.63	$46.65	$46.60
Purchase #5	$60.89	5.188%	$64.049	$64.05	$64.05	$64.00
Purchase #6	$53.28	10.755%	$59.0103	$59.01	$59.00	$59.00
Purchase #7	$10.82	9.325%	$11.829	$11.83	$11.85	$11.80
7 purchase totals =	$481.29		$519.8132	$519.81	$519.85	$519.70