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	$130.46	3.851%	$135.484	$135.48	$135.50	$135.50
Purchase #2	$51.32	6.276%	$54.5408	$54.54	$54.55	$54.50
Purchase #3	$30.88	12.421%	$34.7156	$34.72	$34.70	$34.70
Purchase #4	$76.55	6.409%	$81.4561	$81.46	$81.45	$81.50
Purchase #5	$89.45	6.704%	$95.4467	$95.45	$95.45	$95.40
Purchase #6	$141.31	6.322%	$150.2436	$150.24	$150.25	$150.20
Purchase #7	$123.71	5.566%	$130.5957	$130.60	$130.60	$130.60
7 purchase totals =	$643.68		$682.4825	$682.49	$682.50	$682.40