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	$118.56	7.141%	$127.0264	$127.03	$127.05	$127.00
Purchase #2	$30.51	7.110%	$32.6793	$32.68	$32.70	$32.70
Purchase #3	$176.77	8.770%	$192.2727	$192.27	$192.25	$192.30
Purchase #4	$247.76	10.401%	$273.5295	$273.53	$273.55	$273.50
Purchase #5	$228.77	7.243%	$245.3398	$245.34	$245.35	$245.30
Purchase #6	$89.28	5.855%	$94.5073	$94.51	$94.50	$94.50
Purchase #7	$229.30	11.473%	$255.6076	$255.61	$255.60	$255.60
7 purchase totals =	$1,120.95		$1,220.9626	$1,220.97	$1,221.00	$1,220.90