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	$41.65	11.659%	$46.506	$46.51	$46.50	$46.50
Purchase #2	$224.69	12.129%	$251.9427	$251.94	$251.95	$251.90
Purchase #3	$67.28	7.738%	$72.4861	$72.49	$72.50	$72.50
Purchase #4	$245.34	4.386%	$256.1006	$256.10	$256.10	$256.10
Purchase #5	$130.50	7.524%	$140.3188	$140.32	$140.30	$140.30
Purchase #6	$176.37	10.363%	$194.6472	$194.65	$194.65	$194.60
Purchase #7	$173.72	11.444%	$193.6005	$193.60	$193.60	$193.60
7 purchase totals =	$1,059.55		$1,155.6019	$1,155.61	$1,155.60	$1,155.50