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	$93.90	12.701%	$105.8262	$105.83	$105.85	$105.80
Purchase #2	$61.57	4.471%	$64.3228	$64.32	$64.30	$64.30
Purchase #3	$181.86	9.807%	$199.695	$199.70	$199.70	$199.70
Purchase #4	$106.98	11.588%	$119.3768	$119.38	$119.40	$119.40
Purchase #5	$96.77	8.843%	$105.3274	$105.33	$105.35	$105.30
Purchase #6	$143.78	13.367%	$162.9991	$163.00	$163.00	$163.00
Purchase #7	$235.43	3.231%	$243.0367	$243.04	$243.05	$243.00
7 purchase totals =	$920.29		$1,000.5840	$1,000.60	$1,000.65	$1,000.50