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	$121.25	8.510%	$131.5684	$131.57	$131.55	$131.60
Purchase #2	$186.92	5.190%	$196.6211	$196.62	$196.60	$196.60
Purchase #3	$40.83	5.737%	$43.1724	$43.17	$43.15	$43.20
Purchase #4	$87.36	5.635%	$92.2827	$92.28	$92.30	$92.30
Purchase #5	$119.88	13.123%	$135.6119	$135.61	$135.60	$135.60
Purchase #6	$7.33	7.386%	$7.8714	$7.87	$7.85	$7.90
Purchase #7	$225.45	6.717%	$240.5935	$240.59	$240.60	$240.60
7 purchase totals =	$789.02		$847.7214	$847.71	$847.65	$847.80