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	$48.37	11.660%	$54.0099	$54.01	$54.00	$54.00
Purchase #2	$103.61	7.352%	$111.2274	$111.23	$111.25	$111.20
Purchase #3	$83.62	11.368%	$93.1259	$93.13	$93.15	$93.10
Purchase #4	$198.90	6.224%	$211.2795	$211.28	$211.30	$211.30
Purchase #5	$31.42	13.260%	$35.5863	$35.59	$35.60	$35.60
Purchase #6	$82.73	9.371%	$90.4826	$90.48	$90.50	$90.50
Purchase #7	$247.64	7.704%	$266.7182	$266.72	$266.70	$266.70
7 purchase totals =	$796.29		$862.4298	$862.44	$862.50	$862.40