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	$82.93	4.581%	$86.729	$86.73	$86.75	$86.70
Purchase #2	$80.59	5.596%	$85.0998	$85.10	$85.10	$85.10
Purchase #3	$105.57	5.141%	$110.9974	$111.00	$111.00	$111.00
Purchase #4	$51.31	10.761%	$56.8315	$56.83	$56.85	$56.80
Purchase #5	$5.38	4.651%	$5.6302	$5.63	$5.65	$5.60
Purchase #6	$50.77	7.861%	$54.761	$54.76	$54.75	$54.80
Purchase #7	$151.75	12.672%	$170.9798	$170.98	$171.00	$171.00
7 purchase totals =	$528.30		$571.0287	$571.03	$571.10	$571.00