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	$83.54	9.709%	$91.6509	$91.65	$91.65	$91.70
Purchase #2	$248.54	10.269%	$274.0626	$274.06	$274.05	$274.10
Purchase #3	$87.79	4.745%	$91.9556	$91.96	$91.95	$92.00
Purchase #4	$218.47	8.811%	$237.7194	$237.72	$237.70	$237.70
Purchase #5	$153.55	7.370%	$164.8666	$164.87	$164.85	$164.90
Purchase #6	$152.63	3.769%	$158.3826	$158.38	$158.40	$158.40
Purchase #7	$61.32	6.745%	$65.456	$65.46	$65.45	$65.50
7 purchase totals =	$1,005.84		$1,084.0937	$1,084.10	$1,084.05	$1,084.30