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	$143.89	5.479%	$151.7737	$151.77	$151.75	$151.80
Purchase #2	$36.39	9.228%	$39.7481	$39.75	$39.75	$39.70
Purchase #3	$205.52	6.577%	$219.0371	$219.04	$219.05	$219.00
Purchase #4	$6.70	3.117%	$6.9088	$6.91	$6.90	$6.90
Purchase #5	$86.25	3.568%	$89.3274	$89.33	$89.35	$89.30
Purchase #6	$50.25	6.428%	$53.4801	$53.48	$53.50	$53.50
Purchase #7	$176.84	3.153%	$182.4158	$182.42	$182.40	$182.40
7 purchase totals =	$705.84		$742.6910	$742.70	$742.70	$742.60