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	$190.27	9.602%	$208.5397	$208.54	$208.55	$208.50
Purchase #2	$157.99	13.666%	$179.5809	$179.58	$179.60	$179.60
Purchase #3	$33.92	10.518%	$37.4877	$37.49	$37.50	$37.50
Purchase #4	$78.48	9.126%	$85.6421	$85.64	$85.65	$85.60
Purchase #5	$83.88	9.156%	$91.5601	$91.56	$91.55	$91.60
Purchase #6	$183.75	12.318%	$206.3843	$206.38	$206.40	$206.40
Purchase #7	$71.84	7.539%	$77.256	$77.26	$77.25	$77.30
7 purchase totals =	$800.13		$886.4508	$886.45	$886.50	$886.50