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	$188.69	11.202%	$209.8271	$209.83	$209.85	$209.80
Purchase #2	$69.41	6.374%	$73.8342	$73.83	$73.85	$73.80
Purchase #3	$6.36	4.409%	$6.6404	$6.64	$6.65	$6.60
Purchase #4	$76.86	6.818%	$82.1003	$82.10	$82.10	$82.10
Purchase #5	$204.74	5.265%	$215.5196	$215.52	$215.50	$215.50
Purchase #6	$238.79	9.593%	$261.6971	$261.70	$261.70	$261.70
Purchase #7	$214.40	8.141%	$231.8543	$231.85	$231.85	$231.90
7 purchase totals =	$999.25		$1,081.4730	$1,081.47	$1,081.50	$1,081.40