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	$86.98	9.630%	$95.3562	$95.36	$95.35	$95.40
Purchase #2	$53.65	7.240%	$57.5343	$57.53	$57.55	$57.50
Purchase #3	$88.99	11.158%	$98.9195	$98.92	$98.90	$98.90
Purchase #4	$85.47	4.456%	$89.2785	$89.28	$89.30	$89.30
Purchase #5	$206.27	8.217%	$223.2192	$223.22	$223.20	$223.20
Purchase #6	$137.30	13.656%	$156.0497	$156.05	$156.05	$156.00
Purchase #7	$223.60	9.495%	$244.8308	$244.83	$244.85	$244.80
7 purchase totals =	$882.26		$965.1882	$965.19	$965.20	$965.10