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	$99.62	5.639%	$105.2376	$105.24	$105.25	$105.20
Purchase #2	$120.64	4.265%	$125.7853	$125.79	$125.80	$125.80
Purchase #3	$139.98	11.479%	$156.0483	$156.05	$156.05	$156.00
Purchase #4	$246.91	13.489%	$280.2157	$280.22	$280.20	$280.20
Purchase #5	$132.63	12.170%	$148.7711	$148.77	$148.75	$148.80
Purchase #6	$59.80	12.138%	$67.0585	$67.06	$67.05	$67.10
Purchase #7	$141.51	10.871%	$156.8936	$156.89	$156.90	$156.90
7 purchase totals =	$941.09		$1,040.0101	$1,040.02	$1,040.00	$1,040.00