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	$165.38	10.270%	$182.3645	$182.36	$182.35	$182.40
Purchase #2	$83.76	13.245%	$94.854	$94.85	$94.85	$94.90
Purchase #3	$53.89	4.832%	$56.494	$56.49	$56.50	$56.50
Purchase #4	$44.66	12.227%	$50.1206	$50.12	$50.10	$50.10
Purchase #5	$118.34	6.477%	$126.0049	$126.00	$126.00	$126.00
Purchase #6	$107.35	4.254%	$111.9167	$111.92	$111.90	$111.90
Purchase #7	$128.53	6.312%	$136.6428	$136.64	$136.65	$136.60
7 purchase totals =	$701.91		$758.3975	$758.38	$758.35	$758.40