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	$146.98	6.539%	$156.591	$156.59	$156.60	$156.60
Purchase #2	$145.59	7.454%	$156.4423	$156.44	$156.45	$156.40
Purchase #3	$172.43	4.262%	$179.779	$179.78	$179.80	$179.80
Purchase #4	$173.41	6.473%	$184.6348	$184.63	$184.65	$184.60
Purchase #5	$192.93	12.289%	$216.6392	$216.64	$216.65	$216.60
Purchase #6	$167.97	7.492%	$180.5543	$180.55	$180.55	$180.60
Purchase #7	$41.45	4.650%	$43.3774	$43.38	$43.40	$43.40
7 purchase totals =	$1,040.76		$1,118.0180	$1,118.01	$1,118.10	$1,118.00