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	$105.60	3.548%	$109.3467	$109.35	$109.35	$109.30
Purchase #2	$190.72	5.330%	$200.8854	$200.89	$200.90	$200.90
Purchase #3	$67.40	4.445%	$70.3959	$70.40	$70.40	$70.40
Purchase #4	$142.25	11.283%	$158.3001	$158.30	$158.30	$158.30
Purchase #5	$105.82	3.464%	$109.4856	$109.49	$109.50	$109.50
Purchase #6	$249.26	6.805%	$266.2221	$266.22	$266.20	$266.20
Purchase #7	$218.34	9.633%	$239.3727	$239.37	$239.35	$239.40
7 purchase totals =	$1,079.39		$1,154.0085	$1,154.02	$1,154.00	$1,154.00