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	$39.74	10.585%	$43.9465	$43.95	$43.95	$43.90
Purchase #2	$78.77	13.719%	$89.5765	$89.58	$89.60	$89.60
Purchase #3	$80.32	12.142%	$90.0725	$90.07	$90.05	$90.10
Purchase #4	$202.60	9.103%	$221.0427	$221.04	$221.05	$221.00
Purchase #5	$150.84	13.187%	$170.7313	$170.73	$170.75	$170.70
Purchase #6	$156.54	7.172%	$167.767	$167.77	$167.75	$167.80
Purchase #7	$238.80	13.177%	$270.2667	$270.27	$270.25	$270.30
7 purchase totals =	$947.61		$1,053.4032	$1,053.41	$1,053.40	$1,053.40