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	$172.38	13.259%	$195.2359	$195.24	$195.25	$195.20
Purchase #2	$179.25	3.375%	$185.2997	$185.30	$185.30	$185.30
Purchase #3	$67.39	8.576%	$73.1694	$73.17	$73.15	$73.20
Purchase #4	$85.42	6.284%	$90.7878	$90.79	$90.80	$90.80
Purchase #5	$11.59	8.712%	$12.5997	$12.60	$12.60	$12.60
Purchase #6	$88.92	12.337%	$99.8901	$99.89	$99.90	$99.90
Purchase #7	$146.32	3.829%	$151.9226	$151.92	$151.90	$151.90
7 purchase totals =	$751.27		$808.9052	$808.91	$808.90	$808.90