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	$40.58	9.382%	$44.3872	$44.39	$44.40	$44.40
Purchase #2	$178.36	5.427%	$188.0396	$188.04	$188.05	$188.00
Purchase #3	$151.43	10.342%	$167.0909	$167.09	$167.10	$167.10
Purchase #4	$168.87	3.220%	$174.3076	$174.31	$174.30	$174.30
Purchase #5	$53.57	10.783%	$59.3465	$59.35	$59.35	$59.30
Purchase #6	$42.69	9.806%	$46.8762	$46.88	$46.90	$46.90
Purchase #7	$95.85	5.288%	$100.9185	$100.92	$100.90	$100.90
7 purchase totals =	$731.35		$780.9665	$780.98	$781.00	$780.90