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	$113.36	12.571%	$127.6105	$127.61	$127.60	$127.60
Purchase #2	$227.44	11.694%	$254.0368	$254.04	$254.05	$254.00
Purchase #3	$240.32	10.167%	$264.7533	$264.75	$264.75	$264.80
Purchase #4	$102.80	3.240%	$106.1307	$106.13	$106.15	$106.10
Purchase #5	$100.89	3.846%	$104.7702	$104.77	$104.75	$104.80
Purchase #6	$189.40	13.566%	$215.094	$215.09	$215.10	$215.10
Purchase #7	$158.31	6.361%	$168.3801	$168.38	$168.40	$168.40
7 purchase totals =	$1,132.52		$1,240.7756	$1,240.77	$1,240.80	$1,240.80