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	$93.38	12.398%	$104.9573	$104.96	$104.95	$105.00
Purchase #2	$200.47	10.631%	$221.782	$221.78	$221.80	$221.80
Purchase #3	$181.90	11.150%	$202.1819	$202.18	$202.20	$202.20
Purchase #4	$77.39	5.712%	$81.8105	$81.81	$81.80	$81.80
Purchase #5	$54.54	9.322%	$59.6242	$59.62	$59.60	$59.60
Purchase #6	$28.29	4.713%	$29.6233	$29.62	$29.60	$29.60
Purchase #7	$76.96	7.792%	$82.9567	$82.96	$82.95	$83.00
7 purchase totals =	$712.93		$782.9359	$782.93	$782.90	$783.00