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	$82.87	10.426%	$91.51	$91.51	$91.50	$91.50
Purchase #2	$173.26	8.423%	$187.8537	$187.85	$187.85	$187.90
Purchase #3	$201.55	8.537%	$218.7563	$218.76	$218.75	$218.80
Purchase #4	$103.42	7.659%	$111.3409	$111.34	$111.35	$111.30
Purchase #5	$123.86	9.205%	$135.2613	$135.26	$135.25	$135.30
Purchase #6	$50.34	8.505%	$54.6214	$54.62	$54.60	$54.60
Purchase #7	$195.72	3.853%	$203.2611	$203.26	$203.25	$203.30
7 purchase totals =	$931.02		$1,002.6047	$1,002.60	$1,002.55	$1,002.70