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	$163.58	13.410%	$185.5161	$185.52	$185.50	$185.50
Purchase #2	$10.98	13.415%	$12.453	$12.45	$12.45	$12.50
Purchase #3	$170.50	9.175%	$186.1434	$186.14	$186.15	$186.10
Purchase #4	$105.69	12.608%	$119.0154	$119.02	$119.00	$119.00
Purchase #5	$226.33	13.272%	$256.3685	$256.37	$256.35	$256.40
Purchase #6	$128.60	9.270%	$140.5212	$140.52	$140.50	$140.50
Purchase #7	$41.53	12.117%	$46.5622	$46.56	$46.55	$46.60
7 purchase totals =	$847.21		$946.5798	$946.58	$946.50	$946.60