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	$248.69	11.587%	$277.5057	$277.51	$277.50	$277.50
Purchase #2	$68.32	3.788%	$70.908	$70.91	$70.90	$70.90
Purchase #3	$227.58	10.243%	$250.891	$250.89	$250.90	$250.90
Purchase #4	$136.69	10.122%	$150.5258	$150.53	$150.55	$150.50
Purchase #5	$127.68	11.228%	$142.0159	$142.02	$142.00	$142.00
Purchase #6	$87.42	3.790%	$90.7332	$90.73	$90.75	$90.70
Purchase #7	$189.49	6.294%	$201.4165	$201.42	$201.40	$201.40
7 purchase totals =	$1,085.87		$1,183.9961	$1,184.01	$1,184.00	$1,183.90