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	$60.50	4.694%	$63.3399	$63.34	$63.35	$63.30
Purchase #2	$75.66	3.546%	$78.3429	$78.34	$78.35	$78.30
Purchase #3	$18.45	3.256%	$19.0507	$19.05	$19.05	$19.10
Purchase #4	$76.56	4.614%	$80.0925	$80.09	$80.10	$80.10
Purchase #5	$212.53	3.489%	$219.9452	$219.95	$219.95	$219.90
Purchase #6	$57.82	3.471%	$59.8269	$59.83	$59.85	$59.80
Purchase #7	$38.70	4.524%	$40.4508	$40.45	$40.45	$40.50
7 purchase totals =	$540.22		$561.0489	$561.05	$561.10	$561.00