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	$75.61	3.711%	$78.4159	$78.42	$78.40	$78.40
Purchase #2	$138.59	9.751%	$152.1039	$152.10	$152.10	$152.10
Purchase #3	$36.60	13.594%	$41.5754	$41.58	$41.60	$41.60
Purchase #4	$66.95	6.278%	$71.1531	$71.15	$71.15	$71.20
Purchase #5	$200.98	5.372%	$211.7766	$211.78	$211.80	$211.80
Purchase #6	$239.41	8.680%	$260.1908	$260.19	$260.20	$260.20
Purchase #7	$119.88	6.136%	$127.2358	$127.24	$127.25	$127.20
7 purchase totals =	$878.02		$942.4515	$942.46	$942.50	$942.50