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	$176.86	13.417%	$200.5893	$200.59	$200.60	$200.60
Purchase #2	$57.43	6.741%	$61.3014	$61.30	$61.30	$61.30
Purchase #3	$164.60	10.235%	$181.4468	$181.45	$181.45	$181.40
Purchase #4	$232.67	7.368%	$249.8131	$249.81	$249.80	$249.80
Purchase #5	$119.64	7.272%	$128.3402	$128.34	$128.35	$128.30
Purchase #6	$101.32	12.512%	$113.9972	$114.00	$114.00	$114.00
Purchase #7	$118.29	12.771%	$133.3968	$133.40	$133.40	$133.40
7 purchase totals =	$970.81		$1,068.8848	$1,068.89	$1,068.90	$1,068.80