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	$168.80	12.411%	$189.7498	$189.75	$189.75	$189.70
Purchase #2	$98.79	6.538%	$105.2489	$105.25	$105.25	$105.20
Purchase #3	$178.51	11.614%	$199.2422	$199.24	$199.25	$199.20
Purchase #4	$139.63	6.431%	$148.6096	$148.61	$148.60	$148.60
Purchase #5	$217.32	10.652%	$240.4689	$240.47	$240.45	$240.50
Purchase #6	$40.87	3.344%	$42.2367	$42.24	$42.25	$42.20
Purchase #7	$121.82	11.196%	$135.459	$135.46	$135.45	$135.50
7 purchase totals =	$965.74		$1,061.0151	$1,061.02	$1,061.00	$1,060.90