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	$87.85	4.497%	$91.8006	$91.80	$91.80	$91.80
Purchase #2	$169.32	4.206%	$176.4416	$176.44	$176.45	$176.40
Purchase #3	$67.49	3.161%	$69.6234	$69.62	$69.60	$69.60
Purchase #4	$10.59	4.497%	$11.0662	$11.07	$11.05	$11.10
Purchase #5	$72.36	13.369%	$82.0338	$82.03	$82.05	$82.00
Purchase #6	$26.27	9.699%	$28.8179	$28.82	$28.80	$28.80
Purchase #7	$245.60	4.162%	$255.8219	$255.82	$255.80	$255.80
7 purchase totals =	$679.48		$715.6054	$715.60	$715.55	$715.50