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	$169.98	13.496%	$192.9205	$192.92	$192.90	$192.90
Purchase #2	$185.86	3.583%	$192.5194	$192.52	$192.50	$192.50
Purchase #3	$36.42	3.288%	$37.6175	$37.62	$37.60	$37.60
Purchase #4	$169.61	3.186%	$175.0138	$175.01	$175.00	$175.00
Purchase #5	$97.31	9.313%	$106.3725	$106.37	$106.35	$106.40
Purchase #6	$86.66	10.329%	$95.6111	$95.61	$95.60	$95.60
Purchase #7	$205.72	3.355%	$212.6219	$212.62	$212.60	$212.60
7 purchase totals =	$951.56		$1,012.6767	$1,012.67	$1,012.55	$1,012.60