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	$61.79	9.776%	$67.8306	$67.83	$67.85	$67.80
Purchase #2	$93.39	11.165%	$103.817	$103.82	$103.80	$103.80
Purchase #3	$239.48	4.861%	$251.1211	$251.12	$251.10	$251.10
Purchase #4	$38.90	12.250%	$43.6653	$43.67	$43.65	$43.70
Purchase #5	$160.54	13.301%	$181.8934	$181.89	$181.90	$181.90
Purchase #6	$158.74	12.604%	$178.7476	$178.75	$178.75	$178.70
Purchase #7	$57.68	3.868%	$59.9111	$59.91	$59.90	$59.90
7 purchase totals =	$810.52		$886.9861	$886.99	$886.95	$886.90