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	$170.36	9.541%	$186.614	$186.61	$186.60	$186.60
Purchase #2	$246.86	11.586%	$275.4612	$275.46	$275.45	$275.50
Purchase #3	$66.37	8.684%	$72.1336	$72.13	$72.15	$72.10
Purchase #4	$118.53	6.294%	$125.9903	$125.99	$126.00	$126.00
Purchase #5	$183.40	7.184%	$196.5755	$196.58	$196.60	$196.60
Purchase #6	$148.64	3.829%	$154.3314	$154.33	$154.35	$154.30
Purchase #7	$198.43	6.496%	$211.32	$211.32	$211.30	$211.30
7 purchase totals =	$1,132.59		$1,222.4260	$1,222.42	$1,222.45	$1,222.40