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	$40.60	11.442%	$45.2455	$45.25	$45.25	$45.20
Purchase #2	$36.83	11.580%	$41.0949	$41.09	$41.10	$41.10
Purchase #3	$12.29	6.127%	$13.043	$13.04	$13.05	$13.00
Purchase #4	$156.73	9.647%	$171.8497	$171.85	$171.85	$171.80
Purchase #5	$83.89	7.233%	$89.9578	$89.96	$89.95	$90.00
Purchase #6	$171.46	13.200%	$194.0927	$194.09	$194.10	$194.10
Purchase #7	$167.46	6.772%	$178.8004	$178.80	$178.80	$178.80
7 purchase totals =	$669.26		$734.0840	$734.08	$734.10	$734.00