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	$225.60	7.221%	$241.8906	$241.89	$241.90	$241.90
Purchase #2	$79.49	3.837%	$82.54	$82.54	$82.55	$82.50
Purchase #3	$36.46	9.274%	$39.8413	$39.84	$39.85	$39.80
Purchase #4	$105.40	4.235%	$109.8637	$109.86	$109.85	$109.90
Purchase #5	$29.32	8.244%	$31.7371	$31.74	$31.75	$31.70
Purchase #6	$60.56	9.592%	$66.3689	$66.37	$66.35	$66.40
Purchase #7	$170.67	10.689%	$188.9129	$188.91	$188.90	$188.90
7 purchase totals =	$707.50		$761.1545	$761.15	$761.15	$761.10