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	$162.77	7.136%	$174.3853	$174.39	$174.40	$174.40
Purchase #2	$185.28	7.674%	$199.4984	$199.50	$199.50	$199.50
Purchase #3	$135.37	3.358%	$139.9157	$139.92	$139.90	$139.90
Purchase #4	$245.79	13.805%	$279.7213	$279.72	$279.70	$279.70
Purchase #5	$134.95	6.183%	$143.294	$143.29	$143.30	$143.30
Purchase #6	$185.60	11.254%	$206.4874	$206.49	$206.50	$206.50
Purchase #7	$242.84	13.442%	$275.4826	$275.48	$275.50	$275.50
7 purchase totals =	$1,292.60		$1,418.7847	$1,418.79	$1,418.80	$1,418.80