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	$250.82	5.801%	$265.3701	$265.37	$265.35	$265.40
Purchase #2	$231.67	4.358%	$241.7662	$241.77	$241.75	$241.80
Purchase #3	$98.75	13.333%	$111.9163	$111.92	$111.90	$111.90
Purchase #4	$88.74	13.236%	$100.4856	$100.49	$100.50	$100.50
Purchase #5	$113.62	11.368%	$126.5363	$126.54	$126.55	$126.50
Purchase #6	$158.93	4.380%	$165.8911	$165.89	$165.90	$165.90
Purchase #7	$181.93	6.662%	$194.0502	$194.05	$194.05	$194.10
7 purchase totals =	$1,124.46		$1,206.0158	$1,206.03	$1,206.00	$1,206.10