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	$194.66	12.417%	$218.8309	$218.83	$218.85	$218.80
Purchase #2	$145.45	9.393%	$159.1121	$159.11	$159.10	$159.10
Purchase #3	$151.28	13.831%	$172.2035	$172.20	$172.20	$172.20
Purchase #4	$170.48	5.597%	$180.0218	$180.02	$180.00	$180.00
Purchase #5	$82.72	7.769%	$89.1465	$89.15	$89.15	$89.10
Purchase #6	$116.65	5.511%	$123.0786	$123.08	$123.10	$123.10
Purchase #7	$34.61	9.584%	$37.927	$37.93	$37.95	$37.90
7 purchase totals =	$895.85		$980.3204	$980.32	$980.35	$980.20