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	$150.58	3.664%	$156.0973	$156.10	$156.10	$156.10
Purchase #2	$90.76	8.565%	$98.5336	$98.53	$98.55	$98.50
Purchase #3	$50.81	5.402%	$53.5548	$53.55	$53.55	$53.60
Purchase #4	$134.72	8.857%	$146.6522	$146.65	$146.65	$146.70
Purchase #5	$192.60	9.596%	$211.0819	$211.08	$211.10	$211.10
Purchase #6	$173.44	7.553%	$186.5399	$186.54	$186.55	$186.50
Purchase #7	$119.39	3.795%	$123.9209	$123.92	$123.90	$123.90
7 purchase totals =	$912.30		$976.3806	$976.37	$976.40	$976.40