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	$63.60	7.646%	$68.4629	$68.46	$68.45	$68.50
Purchase #2	$127.94	13.590%	$145.327	$145.33	$145.35	$145.30
Purchase #3	$130.61	8.524%	$141.7432	$141.74	$141.75	$141.70
Purchase #4	$128.41	11.325%	$142.9524	$142.95	$142.95	$143.00
Purchase #5	$197.86	11.832%	$221.2708	$221.27	$221.25	$221.30
Purchase #6	$176.46	6.767%	$188.401	$188.40	$188.40	$188.40
Purchase #7	$90.49	5.764%	$95.7058	$95.71	$95.70	$95.70
7 purchase totals =	$915.37		$1,003.8631	$1,003.86	$1,003.85	$1,003.90