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	$116.81	12.109%	$130.9545	$130.95	$130.95	$131.00
Purchase #2	$176.78	3.522%	$183.0062	$183.01	$183.00	$183.00
Purchase #3	$68.96	7.152%	$73.892	$73.89	$73.90	$73.90
Purchase #4	$127.63	11.700%	$142.5627	$142.56	$142.55	$142.60
Purchase #5	$210.90	13.572%	$239.5233	$239.52	$239.50	$239.50
Purchase #6	$93.54	5.442%	$98.6304	$98.63	$98.65	$98.60
Purchase #7	$206.98	5.546%	$218.4591	$218.46	$218.45	$218.50
7 purchase totals =	$1,001.60		$1,087.0282	$1,087.02	$1,087.00	$1,087.10