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	$91.73	9.847%	$100.7627	$100.76	$100.75	$100.80
Purchase #2	$40.98	9.554%	$44.8952	$44.90	$44.90	$44.90
Purchase #3	$208.53	4.198%	$217.2841	$217.28	$217.30	$217.30
Purchase #4	$233.98	8.327%	$253.4635	$253.46	$253.45	$253.50
Purchase #5	$233.95	12.788%	$263.8675	$263.87	$263.85	$263.90
Purchase #6	$79.88	3.423%	$82.6143	$82.61	$82.60	$82.60
Purchase #7	$189.40	13.764%	$215.469	$215.47	$215.45	$215.50
7 purchase totals =	$1,078.45		$1,178.3563	$1,178.35	$1,178.30	$1,178.50