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	$19.27	6.651%	$20.5516	$20.55	$20.55	$20.60
Purchase #2	$185.80	5.873%	$196.712	$196.71	$196.70	$196.70
Purchase #3	$178.44	7.471%	$191.7713	$191.77	$191.75	$191.80
Purchase #4	$171.33	11.592%	$191.1906	$191.19	$191.20	$191.20
Purchase #5	$126.70	13.216%	$143.4447	$143.44	$143.45	$143.40
Purchase #6	$123.49	12.444%	$138.8571	$138.86	$138.85	$138.90
Purchase #7	$141.77	9.327%	$154.9929	$154.99	$155.00	$155.00
7 purchase totals =	$946.80		$1,037.5202	$1,037.51	$1,037.50	$1,037.60