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	$57.76	3.659%	$59.8734	$59.87	$59.85	$59.90
Purchase #2	$155.47	7.445%	$167.0447	$167.04	$167.05	$167.00
Purchase #3	$164.36	11.238%	$182.8308	$182.83	$182.85	$182.80
Purchase #4	$218.98	10.764%	$242.551	$242.55	$242.55	$242.60
Purchase #5	$24.49	10.272%	$27.0056	$27.01	$27.00	$27.00
Purchase #6	$130.92	9.540%	$143.4098	$143.41	$143.40	$143.40
Purchase #7	$198.49	9.741%	$217.8249	$217.82	$217.80	$217.80
7 purchase totals =	$950.47		$1,040.5402	$1,040.53	$1,040.50	$1,040.50