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	$224.27	12.312%	$251.8821	$251.88	$251.90	$251.90
Purchase #2	$75.89	13.325%	$86.0023	$86.00	$86.00	$86.00
Purchase #3	$78.76	4.864%	$82.5909	$82.59	$82.60	$82.60
Purchase #4	$137.59	13.595%	$156.2954	$156.30	$156.30	$156.30
Purchase #5	$128.53	6.328%	$136.6634	$136.66	$136.65	$136.70
Purchase #6	$188.62	6.562%	$200.9972	$201.00	$201.00	$201.00
Purchase #7	$168.54	7.436%	$181.0726	$181.07	$181.05	$181.10
7 purchase totals =	$1,002.20		$1,095.5039	$1,095.50	$1,095.50	$1,095.60