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	$110.45	7.330%	$118.546	$118.55	$118.55	$118.50
Purchase #2	$38.62	8.195%	$41.7849	$41.78	$41.80	$41.80
Purchase #3	$143.33	6.363%	$152.4501	$152.45	$152.45	$152.50
Purchase #4	$117.91	12.502%	$132.6511	$132.65	$132.65	$132.70
Purchase #5	$123.55	3.120%	$127.4048	$127.40	$127.40	$127.40
Purchase #6	$58.37	4.640%	$61.0784	$61.08	$61.10	$61.10
Purchase #7	$87.55	4.477%	$91.4696	$91.47	$91.45	$91.50
7 purchase totals =	$679.78		$725.3849	$725.38	$725.40	$725.50