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	$55.64	10.517%	$61.4917	$61.49	$61.50	$61.50
Purchase #2	$130.42	9.229%	$142.4565	$142.46	$142.45	$142.50
Purchase #3	$128.46	10.223%	$141.5925	$141.59	$141.60	$141.60
Purchase #4	$122.94	6.867%	$131.3823	$131.38	$131.40	$131.40
Purchase #5	$151.81	11.342%	$169.0283	$169.03	$169.05	$169.00
Purchase #6	$90.55	3.300%	$93.5382	$93.54	$93.55	$93.50
Purchase #7	$240.62	10.711%	$266.3928	$266.39	$266.40	$266.40
7 purchase totals =	$920.44		$1,005.8823	$1,005.88	$1,005.95	$1,005.90