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	$152.34	12.726%	$171.7268	$171.73	$171.75	$171.70
Purchase #2	$169.28	7.392%	$181.7932	$181.79	$181.80	$181.80
Purchase #3	$161.46	12.474%	$181.6005	$181.60	$181.60	$181.60
Purchase #4	$79.45	9.750%	$87.1964	$87.20	$87.20	$87.20
Purchase #5	$177.41	7.192%	$190.1693	$190.17	$190.15	$190.20
Purchase #6	$152.59	4.393%	$159.2933	$159.29	$159.30	$159.30
Purchase #7	$81.62	10.266%	$89.9991	$90.00	$90.00	$90.00
7 purchase totals =	$974.15		$1,061.7786	$1,061.78	$1,061.80	$1,061.80