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	$106.94	10.253%	$117.9046	$117.90	$117.90	$117.90
Purchase #2	$82.35	4.779%	$86.2855	$86.29	$86.30	$86.30
Purchase #3	$241.89	13.748%	$275.145	$275.15	$275.15	$275.10
Purchase #4	$107.25	11.289%	$119.3575	$119.36	$119.35	$119.40
Purchase #5	$194.87	8.231%	$210.9097	$210.91	$210.90	$210.90
Purchase #6	$226.46	4.364%	$236.3427	$236.34	$236.35	$236.30
Purchase #7	$133.83	5.845%	$141.6524	$141.65	$141.65	$141.70
7 purchase totals =	$1,093.59		$1,187.5974	$1,187.60	$1,187.60	$1,187.60