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	$32.56	12.247%	$36.5476	$36.55	$36.55	$36.50
Purchase #2	$190.54	13.367%	$216.0095	$216.01	$216.00	$216.00
Purchase #3	$112.38	5.285%	$118.3193	$118.32	$118.30	$118.30
Purchase #4	$168.48	6.432%	$179.3166	$179.32	$179.30	$179.30
Purchase #5	$92.25	5.608%	$97.4234	$97.42	$97.40	$97.40
Purchase #6	$57.96	12.835%	$65.3992	$65.40	$65.40	$65.40
Purchase #7	$145.45	4.810%	$152.4461	$152.45	$152.45	$152.40
7 purchase totals =	$799.62		$865.4617	$865.47	$865.40	$865.30