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	$226.47	12.307%	$254.3417	$254.34	$254.35	$254.30
Purchase #2	$76.57	5.645%	$80.8924	$80.89	$80.90	$80.90
Purchase #3	$82.50	9.440%	$90.288	$90.29	$90.30	$90.30
Purchase #4	$203.74	3.758%	$211.3965	$211.40	$211.40	$211.40
Purchase #5	$72.44	9.419%	$79.2631	$79.26	$79.25	$79.30
Purchase #6	$230.94	10.659%	$255.5559	$255.56	$255.55	$255.60
Purchase #7	$135.75	3.240%	$140.1483	$140.15	$140.15	$140.10
7 purchase totals =	$1,028.41		$1,111.8859	$1,111.89	$1,111.90	$1,111.90