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	$151.49	4.691%	$158.5964	$158.60	$158.60	$158.60
Purchase #2	$112.65	13.798%	$128.1934	$128.19	$128.20	$128.20
Purchase #3	$25.62	11.873%	$28.6619	$28.66	$28.65	$28.70
Purchase #4	$104.80	9.824%	$115.0956	$115.10	$115.10	$115.10
Purchase #5	$119.33	3.377%	$123.3598	$123.36	$123.35	$123.40
Purchase #6	$190.89	12.678%	$215.091	$215.09	$215.10	$215.10
Purchase #7	$141.91	10.302%	$156.5296	$156.53	$156.55	$156.50
7 purchase totals =	$846.69		$925.5277	$925.53	$925.55	$925.60