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	$102.40	5.368%	$107.8968	$107.90	$107.90	$107.90
Purchase #2	$181.35	3.610%	$187.8967	$187.90	$187.90	$187.90
Purchase #3	$117.28	6.513%	$124.9184	$124.92	$124.90	$124.90
Purchase #4	$55.57	7.226%	$59.5855	$59.59	$59.60	$59.60
Purchase #5	$109.70	6.193%	$116.4937	$116.49	$116.50	$116.50
Purchase #6	$191.78	11.751%	$214.3161	$214.32	$214.30	$214.30
Purchase #7	$240.25	12.765%	$270.9179	$270.92	$270.90	$270.90
7 purchase totals =	$998.33		$1,082.0251	$1,082.04	$1,082.00	$1,082.00