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	$173.96	4.189%	$181.2472	$181.25	$181.25	$181.20
Purchase #2	$225.89	7.651%	$243.1728	$243.17	$243.15	$243.20
Purchase #3	$91.30	4.523%	$95.4295	$95.43	$95.45	$95.40
Purchase #4	$92.49	9.759%	$101.5161	$101.52	$101.50	$101.50
Purchase #5	$11.41	5.637%	$12.0532	$12.05	$12.05	$12.10
Purchase #6	$42.99	5.365%	$45.2964	$45.30	$45.30	$45.30
Purchase #7	$78.72	5.249%	$82.852	$82.85	$82.85	$82.90
7 purchase totals =	$716.76		$761.5672	$761.57	$761.55	$761.60