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	$57.48	8.684%	$62.4716	$62.47	$62.45	$62.50
Purchase #2	$151.53	10.811%	$167.9119	$167.91	$167.90	$167.90
Purchase #3	$98.51	7.173%	$105.5761	$105.58	$105.60	$105.60
Purchase #4	$136.81	3.430%	$141.5026	$141.50	$141.50	$141.50
Purchase #5	$87.36	5.728%	$92.364	$92.36	$92.35	$92.40
Purchase #6	$172.70	8.488%	$187.3588	$187.36	$187.35	$187.40
Purchase #7	$238.34	8.520%	$258.6466	$258.65	$258.65	$258.60
7 purchase totals =	$942.73		$1,015.8316	$1,015.83	$1,015.80	$1,015.90