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	$224.93	10.690%	$248.975	$248.98	$249.00	$249.00
Purchase #2	$229.29	9.798%	$251.7558	$251.76	$251.75	$251.80
Purchase #3	$56.44	4.819%	$59.1598	$59.16	$59.15	$59.20
Purchase #4	$186.77	5.357%	$196.7753	$196.78	$196.80	$196.80
Purchase #5	$159.25	8.572%	$172.9009	$172.90	$172.90	$172.90
Purchase #6	$114.85	10.307%	$126.6876	$126.69	$126.70	$126.70
Purchase #7	$119.65	11.440%	$133.338	$133.34	$133.35	$133.30
7 purchase totals =	$1,091.18		$1,189.5924	$1,189.61	$1,189.65	$1,189.70