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	$189.31	4.596%	$198.0107	$198.01	$198.00	$198.00
Purchase #2	$175.85	3.415%	$181.8553	$181.86	$181.85	$181.90
Purchase #3	$148.30	13.343%	$168.0877	$168.09	$168.10	$168.10
Purchase #4	$120.83	13.657%	$137.3318	$137.33	$137.35	$137.30
Purchase #5	$172.35	8.724%	$187.3858	$187.39	$187.40	$187.40
Purchase #6	$71.59	6.267%	$76.0765	$76.08	$76.10	$76.10
Purchase #7	$99.37	5.287%	$104.6237	$104.62	$104.60	$104.60
7 purchase totals =	$977.60		$1,053.3715	$1,053.38	$1,053.40	$1,053.40