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	$221.26	10.315%	$244.083	$244.08	$244.10	$244.10
Purchase #2	$125.28	8.127%	$135.4615	$135.46	$135.45	$135.50
Purchase #3	$94.56	5.396%	$99.6625	$99.66	$99.65	$99.70
Purchase #4	$119.42	3.347%	$123.417	$123.42	$123.40	$123.40
Purchase #5	$67.68	7.533%	$72.7783	$72.78	$72.80	$72.80
Purchase #6	$36.35	3.405%	$37.5877	$37.59	$37.60	$37.60
Purchase #7	$199.88	3.277%	$206.4301	$206.43	$206.45	$206.40
7 purchase totals =	$864.43		$919.4201	$919.42	$919.45	$919.50