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	$110.59	9.256%	$120.8262	$120.83	$120.85	$120.80
Purchase #2	$147.53	7.115%	$158.0268	$158.03	$158.05	$158.00
Purchase #3	$182.76	3.120%	$188.4621	$188.46	$188.45	$188.50
Purchase #4	$153.53	6.116%	$162.9199	$162.92	$162.90	$162.90
Purchase #5	$243.84	8.551%	$264.6908	$264.69	$264.70	$264.70
Purchase #6	$147.34	6.278%	$156.59	$156.59	$156.60	$156.60
Purchase #7	$108.79	4.340%	$113.5115	$113.51	$113.50	$113.50
7 purchase totals =	$1,094.38		$1,165.0273	$1,165.03	$1,165.05	$1,165.00