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	$168.40	12.847%	$190.0343	$190.03	$190.05	$190.00
Purchase #2	$62.84	8.376%	$68.1035	$68.10	$68.10	$68.10
Purchase #3	$65.39	10.548%	$72.2873	$72.29	$72.30	$72.30
Purchase #4	$136.73	10.269%	$150.7708	$150.77	$150.75	$150.80
Purchase #5	$205.95	8.675%	$223.8162	$223.82	$223.80	$223.80
Purchase #6	$41.62	11.670%	$46.4771	$46.48	$46.50	$46.50
Purchase #7	$140.30	8.755%	$152.5833	$152.58	$152.60	$152.60
7 purchase totals =	$821.23		$904.0725	$904.07	$904.10	$904.10