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	$143.52	5.767%	$151.7968	$151.80	$151.80	$151.80
Purchase #2	$226.43	8.162%	$244.9112	$244.91	$244.90	$244.90
Purchase #3	$204.69	6.787%	$218.5823	$218.58	$218.60	$218.60
Purchase #4	$150.41	5.149%	$158.1546	$158.15	$158.15	$158.20
Purchase #5	$41.63	10.280%	$45.9096	$45.91	$45.90	$45.90
Purchase #6	$163.97	10.527%	$181.2311	$181.23	$181.25	$181.20
Purchase #7	$57.73	3.726%	$59.881	$59.88	$59.90	$59.90
7 purchase totals =	$988.38		$1,060.4666	$1,060.46	$1,060.50	$1,060.50