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	$181.57	11.713%	$202.8373	$202.84	$202.85	$202.80
Purchase #2	$60.92	7.666%	$65.5901	$65.59	$65.60	$65.60
Purchase #3	$38.87	9.269%	$42.4729	$42.47	$42.45	$42.50
Purchase #4	$172.96	7.462%	$185.8663	$185.87	$185.85	$185.90
Purchase #5	$109.52	7.185%	$117.389	$117.39	$117.40	$117.40
Purchase #6	$85.45	4.444%	$89.2474	$89.25	$89.25	$89.20
Purchase #7	$230.71	4.695%	$241.5418	$241.54	$241.55	$241.50
7 purchase totals =	$880.00		$944.9448	$944.95	$944.95	$944.90