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	$243.72	13.677%	$277.0536	$277.05	$277.05	$277.10
Purchase #2	$143.66	12.869%	$162.1476	$162.15	$162.15	$162.10
Purchase #3	$177.53	5.651%	$187.5622	$187.56	$187.55	$187.60
Purchase #4	$95.87	10.338%	$105.781	$105.78	$105.80	$105.80
Purchase #5	$36.77	10.659%	$40.6893	$40.69	$40.70	$40.70
Purchase #6	$167.86	7.386%	$180.2581	$180.26	$180.25	$180.30
Purchase #7	$82.33	8.226%	$89.1025	$89.10	$89.10	$89.10
7 purchase totals =	$947.74		$1,042.5943	$1,042.59	$1,042.60	$1,042.70