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	$186.34	4.392%	$194.5241	$194.52	$194.50	$194.50
Purchase #2	$123.31	3.364%	$127.4581	$127.46	$127.45	$127.50
Purchase #3	$63.26	13.221%	$71.6236	$71.62	$71.60	$71.60
Purchase #4	$122.93	10.752%	$136.1474	$136.15	$136.15	$136.10
Purchase #5	$143.30	4.856%	$150.2586	$150.26	$150.25	$150.30
Purchase #6	$28.26	9.131%	$30.8404	$30.84	$30.85	$30.80
Purchase #7	$106.85	8.547%	$115.9825	$115.98	$116.00	$116.00
7 purchase totals =	$774.25		$826.8347	$826.83	$826.80	$826.80