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	$148.81	4.779%	$155.9216	$155.92	$155.90	$155.90
Purchase #2	$88.93	3.785%	$92.296	$92.30	$92.30	$92.30
Purchase #3	$115.90	5.771%	$122.5886	$122.59	$122.60	$122.60
Purchase #4	$51.40	8.847%	$55.9474	$55.95	$55.95	$55.90
Purchase #5	$73.30	5.789%	$77.5433	$77.54	$77.55	$77.50
Purchase #6	$112.93	9.427%	$123.5759	$123.58	$123.60	$123.60
Purchase #7	$72.64	8.287%	$78.6597	$78.66	$78.65	$78.70
7 purchase totals =	$663.91		$706.5325	$706.54	$706.55	$706.50