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	$97.78	13.574%	$111.0527	$111.05	$111.05	$111.10
Purchase #2	$143.32	6.456%	$152.5727	$152.57	$152.55	$152.60
Purchase #3	$18.76	3.295%	$19.3781	$19.38	$19.40	$19.40
Purchase #4	$75.41	7.311%	$80.9232	$80.92	$80.90	$80.90
Purchase #5	$227.58	9.110%	$248.3125	$248.31	$248.30	$248.30
Purchase #6	$209.87	7.477%	$225.562	$225.56	$225.55	$225.60
Purchase #7	$177.69	5.774%	$187.9498	$187.95	$187.95	$187.90
7 purchase totals =	$950.41		$1,025.7510	$1,025.74	$1,025.70	$1,025.80