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	$93.64	5.611%	$98.8941	$98.89	$98.90	$98.90
Purchase #2	$238.99	10.202%	$263.3718	$263.37	$263.35	$263.40
Purchase #3	$217.32	4.688%	$227.508	$227.51	$227.50	$227.50
Purchase #4	$16.41	8.726%	$17.8419	$17.84	$17.85	$17.80
Purchase #5	$203.54	11.842%	$227.6432	$227.64	$227.65	$227.60
Purchase #6	$47.94	13.547%	$54.4344	$54.43	$54.45	$54.40
Purchase #7	$159.36	7.568%	$171.4204	$171.42	$171.40	$171.40
7 purchase totals =	$977.20		$1,061.1138	$1,061.10	$1,061.10	$1,061.00