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	$206.56	10.498%	$228.2447	$228.24	$228.25	$228.20
Purchase #2	$167.48	3.274%	$172.9633	$172.96	$172.95	$173.00
Purchase #3	$219.39	4.765%	$229.8439	$229.84	$229.85	$229.80
Purchase #4	$114.55	9.143%	$125.0233	$125.02	$125.00	$125.00
Purchase #5	$156.86	9.874%	$172.3484	$172.35	$172.35	$172.30
Purchase #6	$42.73	4.357%	$44.5917	$44.59	$44.60	$44.60
Purchase #7	$39.56	7.436%	$42.5017	$42.50	$42.50	$42.50
7 purchase totals =	$947.13		$1,015.5170	$1,015.50	$1,015.50	$1,015.40