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	$87.61	9.460%	$95.8979	$95.90	$95.90	$95.90
Purchase #2	$52.29	8.219%	$56.5877	$56.59	$56.60	$56.60
Purchase #3	$227.48	10.654%	$251.7157	$251.72	$251.70	$251.70
Purchase #4	$169.94	11.147%	$188.8832	$188.88	$188.90	$188.90
Purchase #5	$89.79	10.349%	$99.0824	$99.08	$99.10	$99.10
Purchase #6	$23.89	6.170%	$25.364	$25.36	$25.35	$25.40
Purchase #7	$178.90	7.573%	$192.4481	$192.45	$192.45	$192.40
7 purchase totals =	$829.90		$909.9790	$909.98	$910.00	$910.00