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	$194.80	4.748%	$204.0491	$204.05	$204.05	$204.00
Purchase #2	$185.30	8.413%	$200.8893	$200.89	$200.90	$200.90
Purchase #3	$56.28	13.243%	$63.7332	$63.73	$63.75	$63.70
Purchase #4	$199.96	7.314%	$214.5851	$214.59	$214.60	$214.60
Purchase #5	$11.86	13.492%	$13.4602	$13.46	$13.45	$13.50
Purchase #6	$67.67	9.204%	$73.8983	$73.90	$73.90	$73.90
Purchase #7	$222.88	12.590%	$250.9406	$250.94	$250.95	$250.90
7 purchase totals =	$938.75		$1,021.5558	$1,021.56	$1,021.60	$1,021.50