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	$180.70	5.861%	$191.2908	$191.29	$191.30	$191.30
Purchase #2	$163.56	11.605%	$182.5411	$182.54	$182.55	$182.50
Purchase #3	$69.75	5.352%	$73.483	$73.48	$73.50	$73.50
Purchase #4	$19.66	6.234%	$20.8856	$20.89	$20.90	$20.90
Purchase #5	$219.89	7.574%	$236.5445	$236.54	$236.55	$236.50
Purchase #6	$148.59	6.445%	$158.1666	$158.17	$158.15	$158.20
Purchase #7	$20.68	3.842%	$21.4745	$21.47	$21.45	$21.50
7 purchase totals =	$822.83		$884.3861	$884.38	$884.40	$884.40