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	$191.96	12.462%	$215.8821	$215.88	$215.90	$215.90
Purchase #2	$18.67	3.630%	$19.3477	$19.35	$19.35	$19.30
Purchase #3	$123.90	3.147%	$127.7991	$127.80	$127.80	$127.80
Purchase #4	$80.26	12.554%	$90.3358	$90.34	$90.35	$90.30
Purchase #5	$102.98	11.378%	$114.6971	$114.70	$114.70	$114.70
Purchase #6	$73.86	3.632%	$76.5426	$76.54	$76.55	$76.50
Purchase #7	$113.72	13.190%	$128.7197	$128.72	$128.70	$128.70
7 purchase totals =	$705.35		$773.3241	$773.33	$773.35	$773.20