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	$182.59	5.430%	$192.5046	$192.50	$192.50	$192.50
Purchase #2	$169.31	6.642%	$180.5556	$180.56	$180.55	$180.60
Purchase #3	$128.44	10.563%	$142.0071	$142.01	$142.00	$142.00
Purchase #4	$94.42	10.463%	$104.2992	$104.30	$104.30	$104.30
Purchase #5	$224.27	4.248%	$233.797	$233.80	$233.80	$233.80
Purchase #6	$42.93	6.157%	$45.5732	$45.57	$45.55	$45.60
Purchase #7	$23.77	7.252%	$25.4938	$25.49	$25.50	$25.50
7 purchase totals =	$865.73		$924.2305	$924.23	$924.20	$924.30