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	$50.43	3.150%	$52.0185	$52.02	$52.00	$52.00
Purchase #2	$218.50	4.467%	$228.2604	$228.26	$228.25	$228.30
Purchase #3	$225.77	6.138%	$239.6278	$239.63	$239.65	$239.60
Purchase #4	$93.92	11.146%	$104.3883	$104.39	$104.40	$104.40
Purchase #5	$202.69	6.265%	$215.3885	$215.39	$215.40	$215.40
Purchase #6	$188.70	4.366%	$196.9386	$196.94	$196.95	$196.90
Purchase #7	$54.81	7.528%	$58.9361	$58.94	$58.95	$58.90
7 purchase totals =	$1,034.82		$1,095.5582	$1,095.57	$1,095.60	$1,095.50