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	$54.70	8.708%	$59.4633	$59.46	$59.45	$59.50
Purchase #2	$13.50	12.822%	$15.231	$15.23	$15.25	$15.20
Purchase #3	$55.44	7.109%	$59.3812	$59.38	$59.40	$59.40
Purchase #4	$218.73	6.650%	$233.2755	$233.28	$233.30	$233.30
Purchase #5	$108.97	6.170%	$115.6934	$115.69	$115.70	$115.70
Purchase #6	$29.55	9.740%	$32.4282	$32.43	$32.45	$32.40
Purchase #7	$243.48	5.582%	$257.0711	$257.07	$257.05	$257.10
7 purchase totals =	$724.37		$772.5437	$772.54	$772.60	$772.60