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	$98.57	13.465%	$111.8425	$111.84	$111.85	$111.80
Purchase #2	$166.69	3.439%	$172.4225	$172.42	$172.40	$172.40
Purchase #3	$107.51	3.785%	$111.5793	$111.58	$111.60	$111.60
Purchase #4	$151.76	3.180%	$156.586	$156.59	$156.60	$156.60
Purchase #5	$213.79	4.521%	$223.4554	$223.46	$223.45	$223.50
Purchase #6	$94.67	10.272%	$104.3945	$104.39	$104.40	$104.40
Purchase #7	$128.44	6.497%	$136.7847	$136.78	$136.80	$136.80
7 purchase totals =	$961.43		$1,017.0649	$1,017.06	$1,017.10	$1,017.10