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	$25.82	5.317%	$27.1928	$27.19	$27.20	$27.20
Purchase #2	$176.92	6.138%	$187.7793	$187.78	$187.80	$187.80
Purchase #3	$194.49	5.470%	$205.1286	$205.13	$205.15	$205.10
Purchase #4	$246.89	6.480%	$262.8885	$262.89	$262.90	$262.90
Purchase #5	$57.50	3.718%	$59.6379	$59.64	$59.65	$59.60
Purchase #6	$33.38	4.341%	$34.829	$34.83	$34.85	$34.80
Purchase #7	$141.73	5.118%	$148.9837	$148.98	$149.00	$149.00
7 purchase totals =	$876.73		$926.4398	$926.44	$926.55	$926.40