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	$52.65	8.740%	$57.2516	$57.25	$57.25	$57.30
Purchase #2	$120.60	3.154%	$124.4037	$124.40	$124.40	$124.40
Purchase #3	$45.97	7.663%	$49.4927	$49.49	$49.50	$49.50
Purchase #4	$82.67	4.564%	$86.4431	$86.44	$86.45	$86.40
Purchase #5	$73.81	12.261%	$82.8598	$82.86	$82.85	$82.90
Purchase #6	$88.46	11.454%	$98.5922	$98.59	$98.60	$98.60
Purchase #7	$67.88	12.661%	$76.4743	$76.47	$76.45	$76.50
7 purchase totals =	$532.04		$575.5174	$575.50	$575.50	$575.60