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	$110.31	7.665%	$118.7653	$118.77	$118.75	$118.80
Purchase #2	$96.69	13.331%	$109.5797	$109.58	$109.60	$109.60
Purchase #3	$223.80	5.230%	$235.5047	$235.50	$235.50	$235.50
Purchase #4	$70.90	8.365%	$76.8308	$76.83	$76.85	$76.80
Purchase #5	$222.89	6.630%	$237.6676	$237.67	$237.65	$237.70
Purchase #6	$120.46	10.563%	$133.1842	$133.18	$133.20	$133.20
Purchase #7	$90.75	9.592%	$99.4547	$99.45	$99.45	$99.50
7 purchase totals =	$935.80		$1,010.9870	$1,010.98	$1,011.00	$1,011.10