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	$47.44	10.460%	$52.4022	$52.40	$52.40	$52.40
Purchase #2	$218.46	6.658%	$233.0051	$233.01	$233.00	$233.00
Purchase #3	$179.39	11.698%	$200.375	$200.38	$200.40	$200.40
Purchase #4	$197.55	13.700%	$224.6144	$224.61	$224.60	$224.60
Purchase #5	$96.72	7.449%	$103.9247	$103.92	$103.90	$103.90
Purchase #6	$88.99	10.659%	$98.4754	$98.48	$98.50	$98.50
Purchase #7	$65.94	3.319%	$68.1285	$68.13	$68.15	$68.10
7 purchase totals =	$894.49		$980.9253	$980.93	$980.95	$980.90