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	$245.99	11.746%	$274.884	$274.88	$274.90	$274.90
Purchase #2	$195.95	6.792%	$209.2589	$209.26	$209.25	$209.30
Purchase #3	$97.66	13.746%	$111.0843	$111.08	$111.10	$111.10
Purchase #4	$48.58	5.795%	$51.3952	$51.40	$51.40	$51.40
Purchase #5	$161.71	6.424%	$172.0983	$172.10	$172.10	$172.10
Purchase #6	$193.49	9.838%	$212.5255	$212.53	$212.55	$212.50
Purchase #7	$35.68	11.789%	$39.8863	$39.89	$39.90	$39.90
7 purchase totals =	$979.06		$1,071.1325	$1,071.14	$1,071.20	$1,071.20