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	$76.39	5.489%	$80.583	$80.58	$80.60	$80.60
Purchase #2	$53.56	10.457%	$59.1608	$59.16	$59.15	$59.20
Purchase #3	$83.52	9.138%	$91.1521	$91.15	$91.15	$91.20
Purchase #4	$168.33	6.336%	$178.9954	$179.00	$179.00	$179.00
Purchase #5	$68.56	5.340%	$72.2211	$72.22	$72.20	$72.20
Purchase #6	$207.59	5.472%	$218.9493	$218.95	$218.95	$218.90
Purchase #7	$240.95	12.656%	$271.4446	$271.44	$271.45	$271.40
7 purchase totals =	$898.90		$972.5063	$972.50	$972.50	$972.50