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	$111.61	4.169%	$116.263	$116.26	$116.25	$116.30
Purchase #2	$59.55	3.374%	$61.5592	$61.56	$61.55	$61.60
Purchase #3	$185.94	6.801%	$198.5858	$198.59	$198.60	$198.60
Purchase #4	$107.97	3.739%	$112.007	$112.01	$112.00	$112.00
Purchase #5	$90.31	4.784%	$94.6304	$94.63	$94.65	$94.60
Purchase #6	$202.66	3.180%	$209.1046	$209.10	$209.10	$209.10
Purchase #7	$121.60	10.696%	$134.6063	$134.61	$134.60	$134.60
7 purchase totals =	$879.64		$926.7563	$926.76	$926.75	$926.80