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	$91.49	13.735%	$104.0562	$104.06	$104.05	$104.10
Purchase #2	$88.96	8.531%	$96.5492	$96.55	$96.55	$96.50
Purchase #3	$113.77	8.545%	$123.4916	$123.49	$123.50	$123.50
Purchase #4	$113.78	3.191%	$117.4107	$117.41	$117.40	$117.40
Purchase #5	$132.39	7.408%	$142.1975	$142.20	$142.20	$142.20
Purchase #6	$199.30	11.694%	$222.6061	$222.61	$222.60	$222.60
Purchase #7	$106.47	10.699%	$117.8612	$117.86	$117.85	$117.90
7 purchase totals =	$846.16		$924.1725	$924.18	$924.15	$924.20