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	$127.46	13.422%	$144.5677	$144.57	$144.55	$144.60
Purchase #2	$202.50	9.620%	$221.9805	$221.98	$222.00	$222.00
Purchase #3	$28.26	12.248%	$31.7213	$31.72	$31.70	$31.70
Purchase #4	$142.41	6.411%	$151.5399	$151.54	$151.55	$151.50
Purchase #5	$115.70	6.586%	$123.32	$123.32	$123.30	$123.30
Purchase #6	$16.29	13.475%	$18.4851	$18.49	$18.50	$18.50
Purchase #7	$218.99	9.386%	$239.5444	$239.54	$239.55	$239.50
7 purchase totals =	$851.61		$931.1589	$931.16	$931.15	$931.10