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	$186.79	8.622%	$202.895	$202.90	$202.90	$202.90
Purchase #2	$203.59	9.371%	$222.6684	$222.67	$222.65	$222.70
Purchase #3	$107.88	10.358%	$119.0542	$119.05	$119.05	$119.10
Purchase #4	$165.74	13.647%	$188.3585	$188.36	$188.35	$188.40
Purchase #5	$201.99	13.331%	$228.9173	$228.92	$228.90	$228.90
Purchase #6	$124.91	5.590%	$131.8925	$131.89	$131.90	$131.90
Purchase #7	$100.63	10.402%	$111.0975	$111.10	$111.10	$111.10
7 purchase totals =	$1,091.53		$1,204.8834	$1,204.89	$1,204.85	$1,205.00