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	$141.29	6.863%	$150.9867	$150.99	$151.00	$151.00
Purchase #2	$79.94	13.625%	$90.8318	$90.83	$90.85	$90.80
Purchase #3	$199.83	3.514%	$206.852	$206.85	$206.85	$206.90
Purchase #4	$180.61	3.107%	$186.2216	$186.22	$186.20	$186.20
Purchase #5	$88.44	4.188%	$92.1439	$92.14	$92.15	$92.10
Purchase #6	$225.58	6.432%	$240.0893	$240.09	$240.10	$240.10
Purchase #7	$73.83	11.653%	$82.4334	$82.43	$82.45	$82.40
7 purchase totals =	$989.52		$1,049.5587	$1,049.55	$1,049.60	$1,049.50