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	$104.43	3.825%	$108.4244	$108.42	$108.40	$108.40
Purchase #2	$77.40	5.274%	$81.4821	$81.48	$81.50	$81.50
Purchase #3	$219.39	10.476%	$242.3733	$242.37	$242.35	$242.40
Purchase #4	$20.33	8.279%	$22.0131	$22.01	$22.00	$22.00
Purchase #5	$246.94	6.861%	$263.8826	$263.88	$263.90	$263.90
Purchase #6	$227.37	5.697%	$240.3233	$240.32	$240.30	$240.30
Purchase #7	$215.80	12.202%	$242.1319	$242.13	$242.15	$242.10
7 purchase totals =	$1,111.66		$1,200.6307	$1,200.61	$1,200.60	$1,200.60