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	$106.86	8.282%	$115.7101	$115.71	$115.70	$115.70
Purchase #2	$148.43	13.316%	$168.1949	$168.19	$168.20	$168.20
Purchase #3	$50.93	10.812%	$56.4366	$56.44	$56.45	$56.40
Purchase #4	$98.45	11.281%	$109.5561	$109.56	$109.55	$109.60
Purchase #5	$95.68	10.752%	$105.9675	$105.97	$105.95	$106.00
Purchase #6	$151.40	3.659%	$156.9397	$156.94	$156.95	$156.90
Purchase #7	$248.77	6.695%	$265.4252	$265.43	$265.45	$265.40
7 purchase totals =	$900.52		$978.2301	$978.24	$978.25	$978.20