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	$168.86	12.789%	$190.4555	$190.46	$190.45	$190.50
Purchase #2	$65.98	10.330%	$72.7957	$72.80	$72.80	$72.80
Purchase #3	$14.57	12.339%	$16.3678	$16.37	$16.35	$16.40
Purchase #4	$40.97	9.838%	$45.0006	$45.00	$45.00	$45.00
Purchase #5	$183.60	4.489%	$191.8418	$191.84	$191.85	$191.80
Purchase #6	$75.90	12.194%	$85.1552	$85.16	$85.15	$85.20
Purchase #7	$220.87	10.339%	$243.7057	$243.71	$243.70	$243.70
7 purchase totals =	$770.75		$845.3223	$845.34	$845.30	$845.40