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	$164.85	4.872%	$172.8815	$172.88	$172.90	$172.90
Purchase #2	$80.72	7.249%	$86.5714	$86.57	$86.55	$86.60
Purchase #3	$113.97	11.781%	$127.3968	$127.40	$127.40	$127.40
Purchase #4	$6.57	8.419%	$7.1231	$7.12	$7.10	$7.10
Purchase #5	$118.44	6.415%	$126.0379	$126.04	$126.05	$126.00
Purchase #6	$235.70	4.830%	$247.0843	$247.08	$247.10	$247.10
Purchase #7	$247.25	9.142%	$269.8536	$269.85	$269.85	$269.90
7 purchase totals =	$967.50		$1,036.9486	$1,036.94	$1,036.95	$1,037.00