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	$34.36	4.191%	$35.8	$35.80	$35.80	$35.80
Purchase #2	$78.72	9.741%	$86.3881	$86.39	$86.40	$86.40
Purchase #3	$52.29	10.359%	$57.7067	$57.71	$57.70	$57.70
Purchase #4	$59.30	5.597%	$62.619	$62.62	$62.60	$62.60
Purchase #5	$246.76	6.774%	$263.4755	$263.48	$263.50	$263.50
Purchase #6	$216.53	9.543%	$237.1935	$237.19	$237.20	$237.20
Purchase #7	$83.95	8.197%	$90.8314	$90.83	$90.85	$90.80
7 purchase totals =	$771.91		$834.0142	$834.02	$834.05	$834.00