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	$167.72	9.547%	$183.7322	$183.73	$183.75	$183.70
Purchase #2	$37.28	12.864%	$42.0757	$42.08	$42.10	$42.10
Purchase #3	$159.31	4.807%	$166.968	$166.97	$166.95	$167.00
Purchase #4	$182.49	8.745%	$198.4488	$198.45	$198.45	$198.40
Purchase #5	$64.36	12.123%	$72.1624	$72.16	$72.15	$72.20
Purchase #6	$94.95	5.509%	$100.1808	$100.18	$100.20	$100.20
Purchase #7	$192.33	12.572%	$216.5097	$216.51	$216.50	$216.50
7 purchase totals =	$898.44		$980.0776	$980.08	$980.10	$980.10