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	$217.86	10.226%	$240.1384	$240.14	$240.15	$240.10
Purchase #2	$98.56	12.841%	$111.2161	$111.22	$111.20	$111.20
Purchase #3	$34.27	4.581%	$35.8399	$35.84	$35.85	$35.80
Purchase #4	$193.81	11.436%	$215.9741	$215.97	$215.95	$216.00
Purchase #5	$83.70	4.411%	$87.392	$87.39	$87.40	$87.40
Purchase #6	$204.39	9.299%	$223.3962	$223.40	$223.40	$223.40
Purchase #7	$168.78	6.225%	$179.2866	$179.29	$179.30	$179.30
7 purchase totals =	$1,001.37		$1,093.2433	$1,093.25	$1,093.25	$1,093.20