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	$144.47	4.427%	$150.8657	$150.87	$150.85	$150.90
Purchase #2	$17.67	6.521%	$18.8223	$18.82	$18.80	$18.80
Purchase #3	$123.83	10.304%	$136.5894	$136.59	$136.60	$136.60
Purchase #4	$57.30	7.285%	$61.4743	$61.47	$61.45	$61.50
Purchase #5	$117.83	4.270%	$122.8613	$122.86	$122.85	$122.90
Purchase #6	$166.78	9.377%	$182.419	$182.42	$182.40	$182.40
Purchase #7	$168.95	9.589%	$185.1506	$185.15	$185.15	$185.20
7 purchase totals =	$796.83		$858.1826	$858.18	$858.10	$858.30