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	$140.75	13.508%	$159.7625	$159.76	$159.75	$159.80
Purchase #2	$250.30	7.792%	$269.8034	$269.80	$269.80	$269.80
Purchase #3	$230.79	6.150%	$244.9836	$244.98	$245.00	$245.00
Purchase #4	$39.99	7.259%	$42.8929	$42.89	$42.90	$42.90
Purchase #5	$95.40	11.317%	$106.1964	$106.20	$106.20	$106.20
Purchase #6	$74.75	5.378%	$78.7701	$78.77	$78.75	$78.80
Purchase #7	$165.87	11.248%	$184.5271	$184.53	$184.55	$184.50
7 purchase totals =	$997.85		$1,086.9360	$1,086.93	$1,086.95	$1,087.00