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	$28.39	9.418%	$31.0638	$31.06	$31.05	$31.10
Purchase #2	$42.60	6.316%	$45.2906	$45.29	$45.30	$45.30
Purchase #3	$178.45	10.308%	$196.8446	$196.84	$196.85	$196.80
Purchase #4	$239.82	11.847%	$268.2315	$268.23	$268.25	$268.20
Purchase #5	$218.74	8.299%	$236.8932	$236.89	$236.90	$236.90
Purchase #6	$175.95	13.130%	$199.0522	$199.05	$199.05	$199.10
Purchase #7	$64.29	7.440%	$69.0732	$69.07	$69.05	$69.10
7 purchase totals =	$948.24		$1,046.4491	$1,046.43	$1,046.45	$1,046.50