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	$175.85	8.396%	$190.6144	$190.61	$190.60	$190.60
Purchase #2	$211.46	11.352%	$235.4649	$235.46	$235.45	$235.50
Purchase #3	$169.89	10.425%	$187.601	$187.60	$187.60	$187.60
Purchase #4	$76.73	6.721%	$81.887	$81.89	$81.90	$81.90
Purchase #5	$103.38	5.713%	$109.2861	$109.29	$109.30	$109.30
Purchase #6	$28.75	9.503%	$31.4821	$31.48	$31.50	$31.50
Purchase #7	$129.91	11.756%	$145.1822	$145.18	$145.20	$145.20
7 purchase totals =	$895.97		$981.5177	$981.51	$981.55	$981.60