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	$188.76	4.319%	$196.9125	$196.91	$196.90	$196.90
Purchase #2	$230.34	10.105%	$253.6159	$253.62	$253.60	$253.60
Purchase #3	$47.66	9.133%	$52.0128	$52.01	$52.00	$52.00
Purchase #4	$191.95	12.148%	$215.2681	$215.27	$215.25	$215.30
Purchase #5	$45.29	8.506%	$49.1424	$49.14	$49.15	$49.10
Purchase #6	$73.34	9.253%	$80.1262	$80.13	$80.15	$80.10
Purchase #7	$25.37	8.573%	$27.545	$27.55	$27.55	$27.50
7 purchase totals =	$802.71		$874.6229	$874.63	$874.60	$874.50