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	$198.59	12.655%	$223.7216	$223.72	$223.70	$223.70
Purchase #2	$119.41	5.656%	$126.1638	$126.16	$126.15	$126.20
Purchase #3	$138.65	3.817%	$143.9423	$143.94	$143.95	$143.90
Purchase #4	$103.36	8.578%	$112.2262	$112.23	$112.25	$112.20
Purchase #5	$205.62	5.501%	$216.9312	$216.93	$216.95	$216.90
Purchase #6	$180.58	8.801%	$196.4728	$196.47	$196.45	$196.50
Purchase #7	$151.69	7.423%	$162.9499	$162.95	$162.95	$162.90
7 purchase totals =	$1,097.90		$1,182.4078	$1,182.40	$1,182.40	$1,182.30