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	$69.56	7.659%	$74.8876	$74.89	$74.90	$74.90
Purchase #2	$33.53	4.821%	$35.1465	$35.15	$35.15	$35.10
Purchase #3	$163.37	6.625%	$174.1933	$174.19	$174.20	$174.20
Purchase #4	$199.57	9.413%	$218.3555	$218.36	$218.35	$218.40
Purchase #5	$195.35	6.734%	$208.5049	$208.50	$208.50	$208.50
Purchase #6	$53.72	11.549%	$59.9241	$59.92	$59.90	$59.90
Purchase #7	$245.53	13.859%	$279.558	$279.56	$279.55	$279.60
7 purchase totals =	$960.63		$1,050.5699	$1,050.57	$1,050.55	$1,050.60