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	$86.42	10.532%	$95.5218	$95.52	$95.50	$95.50
Purchase #2	$84.74	5.688%	$89.56	$89.56	$89.55	$89.60
Purchase #3	$89.25	8.565%	$96.8943	$96.89	$96.90	$96.90
Purchase #4	$203.79	12.311%	$228.8786	$228.88	$228.90	$228.90
Purchase #5	$98.46	13.664%	$111.9136	$111.91	$111.90	$111.90
Purchase #6	$194.62	12.624%	$219.1888	$219.19	$219.20	$219.20
Purchase #7	$233.26	4.153%	$242.9473	$242.95	$242.95	$242.90
7 purchase totals =	$990.54		$1,084.9044	$1,084.90	$1,084.90	$1,084.90