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	$185.48	7.165%	$198.7696	$198.77	$198.75	$198.80
Purchase #2	$31.38	12.760%	$35.3841	$35.38	$35.40	$35.40
Purchase #3	$102.33	11.770%	$114.3742	$114.37	$114.35	$114.40
Purchase #4	$94.75	3.667%	$98.2245	$98.22	$98.20	$98.20
Purchase #5	$16.48	12.531%	$18.5451	$18.55	$18.55	$18.50
Purchase #6	$99.45	5.794%	$105.2121	$105.21	$105.20	$105.20
Purchase #7	$179.37	4.706%	$187.8112	$187.81	$187.80	$187.80
7 purchase totals =	$709.24		$758.3208	$758.31	$758.25	$758.30