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	$102.39	3.193%	$105.6593	$105.66	$105.65	$105.70
Purchase #2	$150.41	10.551%	$166.2798	$166.28	$166.30	$166.30
Purchase #3	$226.83	4.525%	$237.0941	$237.09	$237.10	$237.10
Purchase #4	$143.69	5.791%	$152.0111	$152.01	$152.00	$152.00
Purchase #5	$87.99	13.178%	$99.5853	$99.59	$99.60	$99.60
Purchase #6	$225.34	12.725%	$254.0145	$254.01	$254.00	$254.00
Purchase #7	$59.91	3.440%	$61.9709	$61.97	$61.95	$62.00
7 purchase totals =	$996.56		$1,076.6150	$1,076.61	$1,076.60	$1,076.70