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	$75.61	9.300%	$82.6417	$82.64	$82.65	$82.60
Purchase #2	$12.56	12.362%	$14.1127	$14.11	$14.10	$14.10
Purchase #3	$57.77	8.857%	$62.8867	$62.89	$62.90	$62.90
Purchase #4	$51.48	12.545%	$57.9382	$57.94	$57.95	$57.90
Purchase #5	$111.52	7.562%	$119.9531	$119.95	$119.95	$120.00
Purchase #6	$75.58	3.640%	$78.3311	$78.33	$78.35	$78.30
Purchase #7	$215.54	12.199%	$241.8337	$241.83	$241.85	$241.80
7 purchase totals =	$600.06		$657.6972	$657.69	$657.75	$657.60