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	$128.74	10.757%	$142.5886	$142.59	$142.60	$142.60
Purchase #2	$55.53	7.365%	$59.6198	$59.62	$59.60	$59.60
Purchase #3	$203.90	4.514%	$213.104	$213.10	$213.10	$213.10
Purchase #4	$190.70	7.737%	$205.4545	$205.45	$205.45	$205.50
Purchase #5	$27.73	3.781%	$28.7785	$28.78	$28.80	$28.80
Purchase #6	$17.51	10.187%	$19.2937	$19.29	$19.30	$19.30
Purchase #7	$92.31	6.235%	$98.0655	$98.07	$98.05	$98.10
7 purchase totals =	$716.42		$766.9046	$766.90	$766.90	$767.00