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	$183.33	13.789%	$208.6094	$208.61	$208.60	$208.60
Purchase #2	$173.42	5.139%	$182.3321	$182.33	$182.35	$182.30
Purchase #3	$96.94	6.434%	$103.1771	$103.18	$103.20	$103.20
Purchase #4	$33.85	11.156%	$37.6263	$37.63	$37.65	$37.60
Purchase #5	$76.81	8.511%	$83.3473	$83.35	$83.35	$83.30
Purchase #6	$86.76	10.847%	$96.1709	$96.17	$96.15	$96.20
Purchase #7	$167.35	10.619%	$185.1209	$185.12	$185.10	$185.10
7 purchase totals =	$818.46		$896.3840	$896.39	$896.40	$896.30