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	$233.71	5.111%	$245.6549	$245.65	$245.65	$245.70
Purchase #2	$62.73	7.581%	$67.4856	$67.49	$67.50	$67.50
Purchase #3	$19.75	10.554%	$21.8344	$21.83	$21.85	$21.80
Purchase #4	$131.45	6.302%	$139.734	$139.73	$139.75	$139.70
Purchase #5	$104.30	7.167%	$111.7752	$111.78	$111.80	$111.80
Purchase #6	$61.79	6.134%	$65.5802	$65.58	$65.60	$65.60
Purchase #7	$86.64	12.305%	$97.3011	$97.30	$97.30	$97.30
7 purchase totals =	$700.37		$749.3654	$749.36	$749.45	$749.40