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	$96.32	8.447%	$104.4562	$104.46	$104.45	$104.50
Purchase #2	$199.72	11.873%	$223.4328	$223.43	$223.45	$223.40
Purchase #3	$164.47	11.204%	$182.8972	$182.90	$182.90	$182.90
Purchase #4	$105.25	6.751%	$112.3554	$112.36	$112.35	$112.40
Purchase #5	$156.47	4.181%	$163.012	$163.01	$163.00	$163.00
Purchase #6	$191.88	9.308%	$209.7402	$209.74	$209.75	$209.70
Purchase #7	$59.80	3.453%	$61.8649	$61.86	$61.85	$61.90
7 purchase totals =	$973.91		$1,057.7587	$1,057.76	$1,057.75	$1,057.80