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	$85.43	4.595%	$89.3555	$89.36	$89.35	$89.40
Purchase #2	$182.26	7.661%	$196.2229	$196.22	$196.20	$196.20
Purchase #3	$240.90	4.317%	$251.2997	$251.30	$251.30	$251.30
Purchase #4	$189.89	5.387%	$200.1194	$200.12	$200.10	$200.10
Purchase #5	$113.61	13.492%	$128.9383	$128.94	$128.95	$128.90
Purchase #6	$15.92	8.839%	$17.3272	$17.33	$17.35	$17.30
Purchase #7	$205.27	5.392%	$216.3382	$216.34	$216.35	$216.30
7 purchase totals =	$1,033.28		$1,099.6012	$1,099.61	$1,099.60	$1,099.50