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	$187.31	4.761%	$196.2278	$196.23	$196.25	$196.20
Purchase #2	$139.38	13.323%	$157.9496	$157.95	$157.95	$157.90
Purchase #3	$49.74	4.704%	$52.0798	$52.08	$52.10	$52.10
Purchase #4	$71.74	12.785%	$80.912	$80.91	$80.90	$80.90
Purchase #5	$90.32	5.765%	$95.5269	$95.53	$95.55	$95.50
Purchase #6	$171.79	8.221%	$185.9129	$185.91	$185.90	$185.90
Purchase #7	$79.85	13.813%	$90.8797	$90.88	$90.90	$90.90
7 purchase totals =	$790.13		$859.4887	$859.49	$859.55	$859.40