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	$179.40	9.636%	$196.687	$196.69	$196.70	$196.70
Purchase #2	$56.87	4.150%	$59.2301	$59.23	$59.25	$59.20
Purchase #3	$141.48	13.746%	$160.9278	$160.93	$160.95	$160.90
Purchase #4	$93.43	5.658%	$98.7163	$98.72	$98.70	$98.70
Purchase #5	$226.67	12.572%	$255.167	$255.17	$255.15	$255.20
Purchase #6	$217.94	6.874%	$232.9212	$232.92	$232.90	$232.90
Purchase #7	$161.81	5.463%	$170.6497	$170.65	$170.65	$170.60
7 purchase totals =	$1,077.60		$1,174.2991	$1,174.31	$1,174.30	$1,174.20