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	$235.30	4.105%	$244.9591	$244.96	$244.95	$245.00
Purchase #2	$177.98	10.169%	$196.0788	$196.08	$196.10	$196.10
Purchase #3	$198.63	10.835%	$220.1516	$220.15	$220.15	$220.20
Purchase #4	$82.77	4.252%	$86.2894	$86.29	$86.30	$86.30
Purchase #5	$40.64	3.369%	$42.0092	$42.01	$42.00	$42.00
Purchase #6	$90.51	12.801%	$102.0962	$102.10	$102.10	$102.10
Purchase #7	$50.53	11.742%	$56.4632	$56.46	$56.45	$56.50
7 purchase totals =	$876.36		$948.0475	$948.05	$948.05	$948.20