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	$194.41	5.667%	$205.4272	$205.43	$205.45	$205.40
Purchase #2	$38.75	6.796%	$41.3835	$41.38	$41.40	$41.40
Purchase #3	$84.43	12.802%	$95.2387	$95.24	$95.25	$95.20
Purchase #4	$202.29	10.144%	$222.8103	$222.81	$222.80	$222.80
Purchase #5	$234.30	9.238%	$255.9446	$255.94	$255.95	$255.90
Purchase #6	$138.55	11.438%	$154.3973	$154.40	$154.40	$154.40
Purchase #7	$229.55	12.436%	$258.0968	$258.10	$258.10	$258.10
7 purchase totals =	$1,122.28		$1,233.2984	$1,233.30	$1,233.35	$1,233.20