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	$58.97	6.640%	$62.8856	$62.89	$62.90	$62.90
Purchase #2	$35.73	13.562%	$40.5757	$40.58	$40.60	$40.60
Purchase #3	$90.77	8.459%	$98.4482	$98.45	$98.45	$98.40
Purchase #4	$104.35	9.368%	$114.1255	$114.13	$114.15	$114.10
Purchase #5	$31.77	11.623%	$35.4626	$35.46	$35.45	$35.50
Purchase #6	$67.34	5.369%	$70.9555	$70.96	$70.95	$71.00
Purchase #7	$139.60	5.235%	$146.9081	$146.91	$146.90	$146.90
7 purchase totals =	$528.53		$569.3612	$569.38	$569.40	$569.40