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	$40.56	12.591%	$45.6669	$45.67	$45.65	$45.70
Purchase #2	$71.60	12.195%	$80.3316	$80.33	$80.35	$80.30
Purchase #3	$28.35	12.596%	$31.921	$31.92	$31.90	$31.90
Purchase #4	$209.86	8.772%	$228.2689	$228.27	$228.25	$228.30
Purchase #5	$98.39	5.610%	$103.9097	$103.91	$103.90	$103.90
Purchase #6	$182.81	8.770%	$198.8424	$198.84	$198.85	$198.80
Purchase #7	$74.78	5.273%	$78.7231	$78.72	$78.70	$78.70
7 purchase totals =	$706.35		$767.6636	$767.66	$767.60	$767.60