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	$101.29	12.646%	$114.0991	$114.10	$114.10	$114.10
Purchase #2	$138.99	12.517%	$156.3874	$156.39	$156.40	$156.40
Purchase #3	$225.27	6.488%	$239.8855	$239.89	$239.90	$239.90
Purchase #4	$59.56	4.513%	$62.2479	$62.25	$62.25	$62.20
Purchase #5	$50.54	12.752%	$56.9849	$56.98	$57.00	$57.00
Purchase #6	$79.62	8.180%	$86.1329	$86.13	$86.15	$86.10
Purchase #7	$11.86	5.531%	$12.516	$12.52	$12.50	$12.50
7 purchase totals =	$667.13		$728.2537	$728.26	$728.30	$728.20