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	$214.89	3.535%	$222.4864	$222.49	$222.50	$222.50
Purchase #2	$61.38	10.592%	$67.8814	$67.88	$67.90	$67.90
Purchase #3	$55.45	8.598%	$60.2176	$60.22	$60.20	$60.20
Purchase #4	$117.30	11.587%	$130.8916	$130.89	$130.90	$130.90
Purchase #5	$115.27	11.126%	$128.0949	$128.09	$128.10	$128.10
Purchase #6	$17.85	7.134%	$19.1234	$19.12	$19.10	$19.10
Purchase #7	$187.55	13.646%	$213.1431	$213.14	$213.15	$213.10
7 purchase totals =	$769.69		$841.8384	$841.83	$841.85	$841.80