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	$95.37	6.471%	$101.5414	$101.54	$101.55	$101.50
Purchase #2	$242.47	10.491%	$267.9075	$267.91	$267.90	$267.90
Purchase #3	$163.27	5.802%	$172.7429	$172.74	$172.75	$172.70
Purchase #4	$201.80	7.411%	$216.7554	$216.76	$216.75	$216.80
Purchase #5	$116.58	12.751%	$131.4451	$131.45	$131.45	$131.40
Purchase #6	$64.51	9.868%	$70.8758	$70.88	$70.90	$70.90
Purchase #7	$51.27	7.794%	$55.266	$55.27	$55.25	$55.30
7 purchase totals =	$935.27		$1,016.5341	$1,016.55	$1,016.55	$1,016.50