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	$165.65	13.398%	$187.8438	$187.84	$187.85	$187.80
Purchase #2	$244.60	7.218%	$262.2552	$262.26	$262.25	$262.30
Purchase #3	$102.53	8.509%	$111.2543	$111.25	$111.25	$111.30
Purchase #4	$212.40	11.356%	$236.5201	$236.52	$236.50	$236.50
Purchase #5	$113.69	13.723%	$129.2917	$129.29	$129.30	$129.30
Purchase #6	$41.73	10.201%	$45.9869	$45.99	$46.00	$46.00
Purchase #7	$168.72	13.666%	$191.7773	$191.78	$191.80	$191.80
7 purchase totals =	$1,049.32		$1,164.9293	$1,164.93	$1,164.95	$1,165.00