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	$94.62	11.639%	$105.6328	$105.63	$105.65	$105.60
Purchase #2	$156.83	11.517%	$174.8921	$174.89	$174.90	$174.90
Purchase #3	$80.33	10.852%	$89.0474	$89.05	$89.05	$89.00
Purchase #4	$28.98	6.797%	$30.9498	$30.95	$30.95	$30.90
Purchase #5	$84.27	4.491%	$88.0546	$88.05	$88.05	$88.10
Purchase #6	$185.88	5.437%	$195.9863	$195.99	$196.00	$196.00
Purchase #7	$41.65	10.293%	$45.937	$45.94	$45.95	$45.90
7 purchase totals =	$672.56		$730.5000	$730.50	$730.55	$730.40