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	$133.78	5.439%	$141.0563	$141.06	$141.05	$141.10
Purchase #2	$167.27	6.766%	$178.5875	$178.59	$178.60	$178.60
Purchase #3	$66.94	9.396%	$73.2297	$73.23	$73.25	$73.20
Purchase #4	$150.77	12.441%	$169.5273	$169.53	$169.55	$169.50
Purchase #5	$96.66	8.707%	$105.0762	$105.08	$105.10	$105.10
Purchase #6	$20.41	10.831%	$22.6206	$22.62	$22.60	$22.60
Purchase #7	$120.77	8.623%	$131.184	$131.18	$131.20	$131.20
7 purchase totals =	$756.60		$821.2816	$821.29	$821.35	$821.30