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	$103.46	11.214%	$115.062	$115.06	$115.05	$115.10
Purchase #2	$46.86	10.383%	$51.7255	$51.73	$51.75	$51.70
Purchase #3	$95.44	4.475%	$99.7109	$99.71	$99.70	$99.70
Purchase #4	$104.94	6.505%	$111.7663	$111.77	$111.75	$111.80
Purchase #5	$112.94	5.409%	$119.0489	$119.05	$119.05	$119.00
Purchase #6	$52.55	10.217%	$57.919	$57.92	$57.90	$57.90
Purchase #7	$246.47	5.515%	$260.0628	$260.06	$260.05	$260.10
7 purchase totals =	$762.66		$815.2954	$815.30	$815.25	$815.30