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	$99.31	3.666%	$102.9507	$102.95	$102.95	$103.00
Purchase #2	$132.50	6.715%	$141.3974	$141.40	$141.40	$141.40
Purchase #3	$104.66	9.779%	$114.8947	$114.89	$114.90	$114.90
Purchase #4	$227.51	3.127%	$234.6242	$234.62	$234.60	$234.60
Purchase #5	$52.68	13.409%	$59.7439	$59.74	$59.75	$59.70
Purchase #6	$64.52	11.466%	$71.9179	$71.92	$71.90	$71.90
Purchase #7	$221.47	6.568%	$236.0161	$236.02	$236.00	$236.00
7 purchase totals =	$902.65		$961.5449	$961.54	$961.50	$961.50