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	$63.38	13.228%	$71.7639	$71.76	$71.75	$71.80
Purchase #2	$153.98	9.599%	$168.7605	$168.76	$168.75	$168.80
Purchase #3	$53.30	5.225%	$56.0849	$56.08	$56.10	$56.10
Purchase #4	$71.70	3.544%	$74.241	$74.24	$74.25	$74.20
Purchase #5	$144.45	11.118%	$160.51	$160.51	$160.50	$160.50
Purchase #6	$216.61	8.248%	$234.476	$234.48	$234.50	$234.50
Purchase #7	$39.63	4.828%	$41.5433	$41.54	$41.55	$41.50
7 purchase totals =	$743.05		$807.3796	$807.37	$807.40	$807.40