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	$71.95	8.458%	$78.0355	$78.04	$78.05	$78.00
Purchase #2	$52.34	6.573%	$55.7803	$55.78	$55.80	$55.80
Purchase #3	$180.28	10.366%	$198.9678	$198.97	$198.95	$199.00
Purchase #4	$237.49	11.445%	$264.6707	$264.67	$264.65	$264.70
Purchase #5	$83.36	7.527%	$89.6345	$89.63	$89.65	$89.60
Purchase #6	$218.52	12.770%	$246.425	$246.43	$246.45	$246.40
Purchase #7	$96.52	8.348%	$104.5775	$104.58	$104.60	$104.60
7 purchase totals =	$940.46		$1,038.0913	$1,038.10	$1,038.15	$1,038.10