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	$28.25	9.211%	$30.8521	$30.85	$30.85	$30.90
Purchase #2	$180.89	10.271%	$199.4692	$199.47	$199.45	$199.50
Purchase #3	$207.60	7.704%	$223.5935	$223.59	$223.60	$223.60
Purchase #4	$210.85	3.736%	$218.7274	$218.73	$218.75	$218.70
Purchase #5	$210.37	13.795%	$239.3905	$239.39	$239.40	$239.40
Purchase #6	$71.28	11.532%	$79.5	$79.50	$79.50	$79.50
Purchase #7	$37.39	13.132%	$42.3001	$42.30	$42.30	$42.30
7 purchase totals =	$946.63		$1,033.8328	$1,033.83	$1,033.85	$1,033.90