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	$80.75	5.331%	$85.0548	$85.05	$85.05	$85.10
Purchase #2	$160.63	12.257%	$180.3184	$180.32	$180.30	$180.30
Purchase #3	$50.79	10.399%	$56.0717	$56.07	$56.05	$56.10
Purchase #4	$151.66	10.736%	$167.9422	$167.94	$167.95	$167.90
Purchase #5	$155.25	7.307%	$166.5941	$166.59	$166.60	$166.60
Purchase #6	$177.76	10.679%	$196.743	$196.74	$196.75	$196.70
Purchase #7	$205.46	9.352%	$224.6746	$224.67	$224.65	$224.70
7 purchase totals =	$982.30		$1,077.3988	$1,077.38	$1,077.35	$1,077.40