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	$111.31	7.698%	$119.8786	$119.88	$119.90	$119.90
Purchase #2	$247.68	5.568%	$261.4708	$261.47	$261.45	$261.50
Purchase #3	$115.44	11.467%	$128.6775	$128.68	$128.70	$128.70
Purchase #4	$86.89	3.650%	$90.0615	$90.06	$90.05	$90.10
Purchase #5	$168.42	13.429%	$191.0371	$191.04	$191.05	$191.00
Purchase #6	$52.28	13.386%	$59.2782	$59.28	$59.30	$59.30
Purchase #7	$248.71	4.161%	$259.0588	$259.06	$259.05	$259.10
7 purchase totals =	$1,030.73		$1,109.4625	$1,109.47	$1,109.50	$1,109.60