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	$89.62	11.429%	$99.8627	$99.86	$99.85	$99.90
Purchase #2	$222.54	10.267%	$245.3882	$245.39	$245.40	$245.40
Purchase #3	$45.83	12.654%	$51.6293	$51.63	$51.65	$51.60
Purchase #4	$24.80	6.683%	$26.4574	$26.46	$26.45	$26.50
Purchase #5	$193.45	13.410%	$219.3916	$219.39	$219.40	$219.40
Purchase #6	$197.98	11.106%	$219.9677	$219.97	$219.95	$220.00
Purchase #7	$149.74	4.823%	$156.962	$156.96	$156.95	$157.00
7 purchase totals =	$923.96		$1,019.6589	$1,019.66	$1,019.65	$1,019.80