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	$92.90	8.567%	$100.8587	$100.86	$100.85	$100.90
Purchase #2	$174.64	9.673%	$191.5329	$191.53	$191.55	$191.50
Purchase #3	$99.72	8.831%	$108.5263	$108.53	$108.55	$108.50
Purchase #4	$76.44	7.153%	$81.9078	$81.91	$81.90	$81.90
Purchase #5	$71.29	8.540%	$77.3782	$77.38	$77.40	$77.40
Purchase #6	$15.44	8.608%	$16.7691	$16.77	$16.75	$16.80
Purchase #7	$28.89	9.118%	$31.5242	$31.52	$31.50	$31.50
7 purchase totals =	$559.32		$608.4972	$608.50	$608.50	$608.50