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	$31.36	4.573%	$32.7941	$32.79	$32.80	$32.80
Purchase #2	$164.78	12.457%	$185.3066	$185.31	$185.30	$185.30
Purchase #3	$237.83	4.314%	$248.09	$248.09	$248.10	$248.10
Purchase #4	$73.88	12.773%	$83.3167	$83.32	$83.30	$83.30
Purchase #5	$200.44	3.688%	$207.8322	$207.83	$207.85	$207.80
Purchase #6	$76.43	8.287%	$82.7638	$82.76	$82.75	$82.80
Purchase #7	$243.43	5.847%	$257.6634	$257.66	$257.65	$257.70
7 purchase totals =	$1,028.15		$1,097.7668	$1,097.76	$1,097.75	$1,097.80