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	$145.51	8.321%	$157.6179	$157.62	$157.60	$157.60
Purchase #2	$139.71	3.512%	$144.6166	$144.62	$144.60	$144.60
Purchase #3	$100.88	8.783%	$109.7403	$109.74	$109.75	$109.70
Purchase #4	$164.59	9.651%	$180.4746	$180.47	$180.45	$180.50
Purchase #5	$79.90	12.352%	$89.7692	$89.77	$89.75	$89.80
Purchase #6	$81.38	10.667%	$90.0608	$90.06	$90.05	$90.10
Purchase #7	$188.63	13.118%	$213.3745	$213.37	$213.35	$213.40
7 purchase totals =	$900.60		$985.6539	$985.65	$985.55	$985.70