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	$76.40	3.332%	$78.9456	$78.95	$78.95	$78.90
Purchase #2	$79.83	7.616%	$85.9099	$85.91	$85.90	$85.90
Purchase #3	$169.43	5.848%	$179.3383	$179.34	$179.35	$179.30
Purchase #4	$151.94	6.507%	$161.8267	$161.83	$161.85	$161.80
Purchase #5	$172.97	4.385%	$180.5547	$180.55	$180.55	$180.60
Purchase #6	$250.39	12.544%	$281.7989	$281.80	$281.80	$281.80
Purchase #7	$134.41	7.789%	$144.8792	$144.88	$144.90	$144.90
7 purchase totals =	$1,035.37		$1,113.2533	$1,113.26	$1,113.30	$1,113.20