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	$10.38	13.414%	$11.7724	$11.77	$11.75	$11.80
Purchase #2	$59.48	3.182%	$61.3727	$61.37	$61.35	$61.40
Purchase #3	$141.44	7.872%	$152.5742	$152.57	$152.55	$152.60
Purchase #4	$143.61	9.204%	$156.8279	$156.83	$156.85	$156.80
Purchase #5	$131.83	7.683%	$141.9585	$141.96	$141.95	$142.00
Purchase #6	$165.54	9.836%	$181.8225	$181.82	$181.80	$181.80
Purchase #7	$24.65	9.611%	$27.0191	$27.02	$27.00	$27.00
7 purchase totals =	$676.93		$733.3473	$733.34	$733.25	$733.40