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	$127.36	5.541%	$134.417	$134.42	$134.40	$134.40
Purchase #2	$186.65	9.375%	$204.1484	$204.15	$204.15	$204.10
Purchase #3	$98.46	11.311%	$109.5968	$109.60	$109.60	$109.60
Purchase #4	$232.89	11.436%	$259.5233	$259.52	$259.50	$259.50
Purchase #5	$203.43	9.569%	$222.8962	$222.90	$222.90	$222.90
Purchase #6	$200.60	13.822%	$228.3269	$228.33	$228.35	$228.30
Purchase #7	$162.31	12.193%	$182.1005	$182.10	$182.10	$182.10
7 purchase totals =	$1,211.70		$1,341.0091	$1,341.02	$1,341.00	$1,340.90