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	$129.95	7.107%	$139.1855	$139.19	$139.20	$139.20
Purchase #2	$179.32	6.529%	$191.0278	$191.03	$191.05	$191.00
Purchase #3	$107.83	4.627%	$112.8193	$112.82	$112.80	$112.80
Purchase #4	$186.92	7.466%	$200.8754	$200.88	$200.90	$200.90
Purchase #5	$90.61	7.435%	$97.3469	$97.35	$97.35	$97.30
Purchase #6	$207.78	12.543%	$233.8418	$233.84	$233.85	$233.80
Purchase #7	$33.48	7.353%	$35.9418	$35.94	$35.95	$35.90
7 purchase totals =	$935.89		$1,011.0385	$1,011.05	$1,011.10	$1,010.90