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	$196.47	3.240%	$202.8356	$202.84	$202.85	$202.80
Purchase #2	$111.98	13.669%	$127.2865	$127.29	$127.30	$127.30
Purchase #3	$133.97	10.822%	$148.4682	$148.47	$148.45	$148.50
Purchase #4	$32.50	9.156%	$35.4757	$35.48	$35.50	$35.50
Purchase #5	$188.42	9.246%	$205.8413	$205.84	$205.85	$205.80
Purchase #6	$39.53	7.854%	$42.6347	$42.63	$42.65	$42.60
Purchase #7	$63.80	10.761%	$70.6655	$70.67	$70.65	$70.70
7 purchase totals =	$766.67		$833.2075	$833.22	$833.25	$833.20