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	$181.40	8.218%	$196.3075	$196.31	$196.30	$196.30
Purchase #2	$101.30	3.318%	$104.6611	$104.66	$104.65	$104.70
Purchase #3	$71.97	6.688%	$76.7834	$76.78	$76.80	$76.80
Purchase #4	$101.66	7.798%	$109.5874	$109.59	$109.60	$109.60
Purchase #5	$183.81	8.743%	$199.8805	$199.88	$199.90	$199.90
Purchase #6	$35.85	7.132%	$38.4068	$38.41	$38.40	$38.40
Purchase #7	$5.44	12.731%	$6.1326	$6.13	$6.15	$6.10
7 purchase totals =	$681.43		$731.7593	$731.76	$731.80	$731.80