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	$105.76	7.374%	$113.5587	$113.56	$113.55	$113.60
Purchase #2	$111.69	10.826%	$123.7816	$123.78	$123.80	$123.80
Purchase #3	$42.60	4.576%	$44.5494	$44.55	$44.55	$44.50
Purchase #4	$97.53	12.406%	$109.6296	$109.63	$109.65	$109.60
Purchase #5	$11.59	13.366%	$13.1391	$13.14	$13.15	$13.10
Purchase #6	$39.94	13.788%	$45.4469	$45.45	$45.45	$45.40
Purchase #7	$247.73	3.452%	$256.2816	$256.28	$256.30	$256.30
7 purchase totals =	$656.84		$706.3869	$706.39	$706.45	$706.30