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	$169.78	5.754%	$179.5491	$179.55	$179.55	$179.50
Purchase #2	$152.74	9.401%	$167.0991	$167.10	$167.10	$167.10
Purchase #3	$240.38	6.328%	$255.5912	$255.59	$255.60	$255.60
Purchase #4	$48.77	3.545%	$50.4989	$50.50	$50.50	$50.50
Purchase #5	$145.89	8.229%	$157.8953	$157.90	$157.90	$157.90
Purchase #6	$51.74	6.431%	$55.0674	$55.07	$55.05	$55.10
Purchase #7	$162.38	5.563%	$171.4132	$171.41	$171.40	$171.40
7 purchase totals =	$971.68		$1,037.1142	$1,037.12	$1,037.10	$1,037.10