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	$127.56	9.404%	$139.5557	$139.56	$139.55	$139.60
Purchase #2	$38.36	11.300%	$42.6947	$42.69	$42.70	$42.70
Purchase #3	$5.36	13.826%	$6.1011	$6.10	$6.10	$6.10
Purchase #4	$185.53	13.603%	$210.7676	$210.77	$210.75	$210.80
Purchase #5	$176.35	5.844%	$186.6559	$186.66	$186.65	$186.70
Purchase #6	$167.42	9.586%	$183.4689	$183.47	$183.45	$183.50
Purchase #7	$239.66	10.179%	$264.055	$264.06	$264.05	$264.10
7 purchase totals =	$940.24		$1,033.2989	$1,033.31	$1,033.25	$1,033.50