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	$130.98	10.266%	$144.4264	$144.43	$144.45	$144.40
Purchase #2	$131.85	7.246%	$141.4039	$141.40	$141.40	$141.40
Purchase #3	$246.60	7.759%	$265.7337	$265.73	$265.75	$265.70
Purchase #4	$19.35	4.527%	$20.226	$20.23	$20.25	$20.20
Purchase #5	$48.90	8.242%	$52.9303	$52.93	$52.95	$52.90
Purchase #6	$221.90	4.365%	$231.5859	$231.59	$231.60	$231.60
Purchase #7	$196.88	6.557%	$209.7894	$209.79	$209.80	$209.80
7 purchase totals =	$996.46		$1,066.0956	$1,066.10	$1,066.20	$1,066.00