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	$12.54	11.731%	$14.0111	$14.01	$14.00	$14.00
Purchase #2	$107.98	3.642%	$111.9126	$111.91	$111.90	$111.90
Purchase #3	$174.74	12.706%	$196.9425	$196.94	$196.95	$196.90
Purchase #4	$89.59	6.181%	$95.1276	$95.13	$95.15	$95.10
Purchase #5	$21.33	5.104%	$22.4187	$22.42	$22.40	$22.40
Purchase #6	$54.34	9.365%	$59.4289	$59.43	$59.45	$59.40
Purchase #7	$203.25	10.280%	$224.1441	$224.14	$224.15	$224.10
7 purchase totals =	$663.77		$723.9855	$723.98	$724.00	$723.80