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	$167.99	13.270%	$190.2823	$190.28	$190.30	$190.30
Purchase #2	$85.52	6.452%	$91.0378	$91.04	$91.05	$91.00
Purchase #3	$85.85	13.828%	$97.7213	$97.72	$97.70	$97.70
Purchase #4	$12.43	6.590%	$13.2491	$13.25	$13.25	$13.20
Purchase #5	$232.85	3.621%	$241.2815	$241.28	$241.30	$241.30
Purchase #6	$243.77	9.551%	$267.0525	$267.05	$267.05	$267.10
Purchase #7	$98.84	10.171%	$108.893	$108.89	$108.90	$108.90
7 purchase totals =	$927.25		$1,009.5175	$1,009.51	$1,009.55	$1,009.50