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	$101.77	12.147%	$114.132	$114.13	$114.15	$114.10
Purchase #2	$49.72	8.700%	$54.0456	$54.05	$54.05	$54.00
Purchase #3	$206.64	4.391%	$215.7136	$215.71	$215.70	$215.70
Purchase #4	$206.59	7.493%	$222.0698	$222.07	$222.05	$222.10
Purchase #5	$59.96	6.398%	$63.7962	$63.80	$63.80	$63.80
Purchase #6	$173.86	12.104%	$194.904	$194.90	$194.90	$194.90
Purchase #7	$32.51	10.248%	$35.8416	$35.84	$35.85	$35.80
7 purchase totals =	$831.05		$900.5028	$900.50	$900.50	$900.40