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	$33.69	4.526%	$35.2148	$35.21	$35.20	$35.20
Purchase #2	$154.39	5.356%	$162.6591	$162.66	$162.65	$162.70
Purchase #3	$211.54	6.442%	$225.1674	$225.17	$225.15	$225.20
Purchase #4	$87.60	3.801%	$90.9297	$90.93	$90.95	$90.90
Purchase #5	$216.82	3.126%	$223.5978	$223.60	$223.60	$223.60
Purchase #6	$212.85	9.331%	$232.711	$232.71	$232.70	$232.70
Purchase #7	$238.92	13.818%	$271.934	$271.93	$271.95	$271.90
7 purchase totals =	$1,155.81		$1,242.2138	$1,242.21	$1,242.20	$1,242.20