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	$109.75	12.618%	$123.5983	$123.60	$123.60	$123.60
Purchase #2	$32.26	4.280%	$33.6407	$33.64	$33.65	$33.60
Purchase #3	$77.38	4.386%	$80.7739	$80.77	$80.75	$80.80
Purchase #4	$134.88	5.725%	$142.6019	$142.60	$142.60	$142.60
Purchase #5	$167.85	7.711%	$180.7929	$180.79	$180.80	$180.80
Purchase #6	$100.79	9.633%	$110.4991	$110.50	$110.50	$110.50
Purchase #7	$26.40	12.236%	$29.6303	$29.63	$29.65	$29.60
7 purchase totals =	$649.31		$701.5371	$701.53	$701.55	$701.50