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	$168.76	4.338%	$176.0808	$176.08	$176.10	$176.10
Purchase #2	$51.51	7.684%	$55.468	$55.47	$55.45	$55.50
Purchase #3	$98.97	4.791%	$103.7117	$103.71	$103.70	$103.70
Purchase #4	$102.45	3.380%	$105.9128	$105.91	$105.90	$105.90
Purchase #5	$104.89	6.291%	$111.4886	$111.49	$111.50	$111.50
Purchase #6	$141.33	13.626%	$160.5876	$160.59	$160.60	$160.60
Purchase #7	$62.58	13.761%	$71.1916	$71.19	$71.20	$71.20
7 purchase totals =	$730.49		$784.4411	$784.44	$784.45	$784.50