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	$70.71	5.528%	$74.6188	$74.62	$74.60	$74.60
Purchase #2	$134.37	7.156%	$143.9855	$143.99	$144.00	$144.00
Purchase #3	$192.96	12.266%	$216.6285	$216.63	$216.65	$216.60
Purchase #4	$142.33	3.849%	$147.8083	$147.81	$147.80	$147.80
Purchase #5	$198.55	12.476%	$223.3211	$223.32	$223.30	$223.30
Purchase #6	$231.32	7.454%	$248.5626	$248.56	$248.55	$248.60
Purchase #7	$80.90	12.343%	$90.8855	$90.89	$90.90	$90.90
7 purchase totals =	$1,051.14		$1,145.8103	$1,145.82	$1,145.80	$1,145.80