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	$72.58	7.308%	$77.8841	$77.88	$77.90	$77.90
Purchase #2	$210.81	12.684%	$237.5491	$237.55	$237.55	$237.50
Purchase #3	$90.92	7.181%	$97.449	$97.45	$97.45	$97.40
Purchase #4	$219.85	6.841%	$234.8899	$234.89	$234.90	$234.90
Purchase #5	$151.73	4.187%	$158.0829	$158.08	$158.10	$158.10
Purchase #6	$40.34	10.850%	$44.7169	$44.72	$44.70	$44.70
Purchase #7	$152.77	12.484%	$171.8418	$171.84	$171.85	$171.80
7 purchase totals =	$939.00		$1,022.4137	$1,022.41	$1,022.45	$1,022.30