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	$236.89	7.381%	$254.3749	$254.37	$254.35	$254.40
Purchase #2	$160.88	11.848%	$179.9411	$179.94	$179.95	$179.90
Purchase #3	$180.86	5.872%	$191.4801	$191.48	$191.50	$191.50
Purchase #4	$213.37	12.738%	$240.5491	$240.55	$240.55	$240.50
Purchase #5	$92.71	11.532%	$103.4013	$103.40	$103.40	$103.40
Purchase #6	$5.58	8.638%	$6.062	$6.06	$6.05	$6.10
Purchase #7	$44.40	4.508%	$46.4016	$46.40	$46.40	$46.40
7 purchase totals =	$934.69		$1,022.2101	$1,022.20	$1,022.20	$1,022.20