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	$216.97	10.113%	$238.9122	$238.91	$238.90	$238.90
Purchase #2	$118.40	8.386%	$128.329	$128.33	$128.35	$128.30
Purchase #3	$61.72	13.675%	$70.1602	$70.16	$70.15	$70.20
Purchase #4	$89.64	9.848%	$98.4677	$98.47	$98.45	$98.50
Purchase #5	$33.90	5.628%	$35.8079	$35.81	$35.80	$35.80
Purchase #6	$83.36	12.815%	$94.0426	$94.04	$94.05	$94.00
Purchase #7	$144.67	12.596%	$162.8926	$162.89	$162.90	$162.90
7 purchase totals =	$748.66		$828.6122	$828.61	$828.60	$828.60