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	$196.41	11.690%	$219.3703	$219.37	$219.35	$219.40
Purchase #2	$180.77	10.385%	$199.543	$199.54	$199.55	$199.50
Purchase #3	$96.38	3.357%	$99.6155	$99.62	$99.60	$99.60
Purchase #4	$131.38	9.405%	$143.7363	$143.74	$143.75	$143.70
Purchase #5	$100.85	7.564%	$108.4783	$108.48	$108.50	$108.50
Purchase #6	$250.34	6.417%	$266.4043	$266.40	$266.40	$266.40
Purchase #7	$167.31	7.371%	$179.6424	$179.64	$179.65	$179.60
7 purchase totals =	$1,123.44		$1,216.7901	$1,216.79	$1,216.80	$1,216.70