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	$141.36	12.137%	$158.5169	$158.52	$158.50	$158.50
Purchase #2	$40.77	7.325%	$43.7564	$43.76	$43.75	$43.80
Purchase #3	$162.86	3.217%	$168.0992	$168.10	$168.10	$168.10
Purchase #4	$55.65	4.314%	$58.0507	$58.05	$58.05	$58.10
Purchase #5	$116.63	4.501%	$121.8795	$121.88	$121.90	$121.90
Purchase #6	$36.86	12.799%	$41.5777	$41.58	$41.60	$41.60
Purchase #7	$117.33	13.783%	$133.5016	$133.50	$133.50	$133.50
7 purchase totals =	$671.46		$725.3820	$725.39	$725.40	$725.50