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	$70.77	6.586%	$75.4309	$75.43	$75.45	$75.40
Purchase #2	$111.53	12.641%	$125.6285	$125.63	$125.65	$125.60
Purchase #3	$205.82	9.746%	$225.8792	$225.88	$225.90	$225.90
Purchase #4	$6.92	9.430%	$7.5726	$7.57	$7.55	$7.60
Purchase #5	$52.82	12.609%	$59.4801	$59.48	$59.50	$59.50
Purchase #6	$46.34	5.562%	$48.9174	$48.92	$48.90	$48.90
Purchase #7	$170.82	6.774%	$182.3913	$182.39	$182.40	$182.40
7 purchase totals =	$665.02		$725.3000	$725.30	$725.35	$725.30