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	$170.81	9.228%	$186.5723	$186.57	$186.55	$186.60
Purchase #2	$128.96	5.657%	$136.2553	$136.26	$136.25	$136.30
Purchase #3	$89.48	4.538%	$93.5406	$93.54	$93.55	$93.50
Purchase #4	$157.96	12.631%	$177.9119	$177.91	$177.90	$177.90
Purchase #5	$83.50	6.561%	$88.9784	$88.98	$89.00	$89.00
Purchase #6	$178.59	3.688%	$185.1764	$185.18	$185.20	$185.20
Purchase #7	$130.84	11.115%	$145.3829	$145.38	$145.40	$145.40
7 purchase totals =	$940.14		$1,013.8178	$1,013.82	$1,013.85	$1,013.90