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	$106.26	7.703%	$114.4452	$114.45	$114.45	$114.40
Purchase #2	$125.30	5.176%	$131.7855	$131.79	$131.80	$131.80
Purchase #3	$175.36	12.120%	$196.6136	$196.61	$196.60	$196.60
Purchase #4	$212.92	4.321%	$222.1203	$222.12	$222.10	$222.10
Purchase #5	$34.64	5.700%	$36.6145	$36.61	$36.60	$36.60
Purchase #6	$174.61	9.626%	$191.418	$191.42	$191.40	$191.40
Purchase #7	$51.27	5.569%	$54.1252	$54.13	$54.15	$54.10
7 purchase totals =	$880.36		$947.1223	$947.13	$947.10	$947.00