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	$85.88	3.200%	$88.6282	$88.63	$88.65	$88.60
Purchase #2	$144.52	8.376%	$156.625	$156.63	$156.65	$156.60
Purchase #3	$30.88	4.456%	$32.256	$32.26	$32.25	$32.30
Purchase #4	$225.76	3.410%	$233.4584	$233.46	$233.45	$233.50
Purchase #5	$113.53	4.164%	$118.2574	$118.26	$118.25	$118.30
Purchase #6	$192.83	11.760%	$215.5068	$215.51	$215.50	$215.50
Purchase #7	$198.57	6.129%	$210.7404	$210.74	$210.75	$210.70
7 purchase totals =	$991.97		$1,055.4722	$1,055.49	$1,055.50	$1,055.50