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	$236.78	7.254%	$253.956	$253.96	$253.95	$254.00
Purchase #2	$240.59	7.462%	$258.5428	$258.54	$258.55	$258.50
Purchase #3	$71.88	8.794%	$78.2011	$78.20	$78.20	$78.20
Purchase #4	$83.69	12.621%	$94.2525	$94.25	$94.25	$94.30
Purchase #5	$6.96	13.325%	$7.8874	$7.89	$7.90	$7.90
Purchase #6	$170.62	5.228%	$179.54	$179.54	$179.55	$179.50
Purchase #7	$71.50	3.321%	$73.8745	$73.87	$73.85	$73.90
7 purchase totals =	$882.02		$946.2543	$946.25	$946.25	$946.30