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	$224.83	8.339%	$243.5786	$243.58	$243.60	$243.60
Purchase #2	$164.77	13.311%	$186.7025	$186.70	$186.70	$186.70
Purchase #3	$56.64	4.865%	$59.3955	$59.40	$59.40	$59.40
Purchase #4	$90.51	12.223%	$101.573	$101.57	$101.55	$101.60
Purchase #5	$187.62	12.800%	$211.6354	$211.64	$211.65	$211.60
Purchase #6	$162.43	10.567%	$179.594	$179.59	$179.60	$179.60
Purchase #7	$175.30	13.228%	$198.4887	$198.49	$198.50	$198.50
7 purchase totals =	$1,062.10		$1,180.9677	$1,180.97	$1,181.00	$1,181.00