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	$119.42	3.724%	$123.8672	$123.87	$123.85	$123.90
Purchase #2	$139.58	10.709%	$154.5276	$154.53	$154.55	$154.50
Purchase #3	$105.84	9.411%	$115.8006	$115.80	$115.80	$115.80
Purchase #4	$121.45	7.364%	$130.3936	$130.39	$130.40	$130.40
Purchase #5	$89.42	11.313%	$99.5361	$99.54	$99.55	$99.50
Purchase #6	$88.46	3.776%	$91.8002	$91.80	$91.80	$91.80
Purchase #7	$17.48	4.682%	$18.2984	$18.30	$18.30	$18.30
7 purchase totals =	$681.65		$734.2237	$734.23	$734.25	$734.20