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	$171.76	8.401%	$186.1896	$186.19	$186.20	$186.20
Purchase #2	$164.61	4.277%	$171.6504	$171.65	$171.65	$171.70
Purchase #3	$32.92	12.537%	$37.0472	$37.05	$37.05	$37.00
Purchase #4	$161.67	10.486%	$178.6227	$178.62	$178.60	$178.60
Purchase #5	$245.69	3.592%	$254.5152	$254.52	$254.50	$254.50
Purchase #6	$42.93	8.471%	$46.5666	$46.57	$46.55	$46.60
Purchase #7	$185.76	13.616%	$211.0531	$211.05	$211.05	$211.10
7 purchase totals =	$1,005.34		$1,085.6448	$1,085.65	$1,085.60	$1,085.70