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	$82.44	6.218%	$87.5661	$87.57	$87.55	$87.60
Purchase #2	$246.88	11.762%	$275.918	$275.92	$275.90	$275.90
Purchase #3	$166.70	3.270%	$172.1511	$172.15	$172.15	$172.20
Purchase #4	$136.49	5.593%	$144.1239	$144.12	$144.10	$144.10
Purchase #5	$209.55	6.364%	$222.8858	$222.89	$222.90	$222.90
Purchase #6	$225.46	3.194%	$232.6612	$232.66	$232.65	$232.70
Purchase #7	$132.39	13.585%	$150.3752	$150.38	$150.40	$150.40
7 purchase totals =	$1,199.91		$1,285.6813	$1,285.69	$1,285.65	$1,285.80