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	$145.30	11.385%	$161.8424	$161.84	$161.85	$161.80
Purchase #2	$240.32	6.651%	$256.3037	$256.30	$256.30	$256.30
Purchase #3	$104.99	13.663%	$119.3348	$119.33	$119.35	$119.30
Purchase #4	$186.30	7.628%	$200.511	$200.51	$200.50	$200.50
Purchase #5	$154.54	11.212%	$171.867	$171.87	$171.85	$171.90
Purchase #6	$29.32	13.468%	$33.2688	$33.27	$33.25	$33.30
Purchase #7	$120.71	4.435%	$126.0635	$126.06	$126.05	$126.10
7 purchase totals =	$981.48		$1,069.1912	$1,069.18	$1,069.15	$1,069.20