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	$201.96	8.269%	$218.6601	$218.66	$218.65	$218.70
Purchase #2	$18.86	8.548%	$20.4722	$20.47	$20.45	$20.50
Purchase #3	$42.80	7.213%	$45.8872	$45.89	$45.90	$45.90
Purchase #4	$139.41	11.523%	$155.4742	$155.47	$155.45	$155.50
Purchase #5	$228.85	4.187%	$238.4319	$238.43	$238.45	$238.40
Purchase #6	$182.69	9.432%	$199.9213	$199.92	$199.90	$199.90
Purchase #7	$91.41	12.400%	$102.7448	$102.74	$102.75	$102.70
7 purchase totals =	$905.98		$981.5917	$981.58	$981.55	$981.60