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	$197.61	6.368%	$210.1938	$210.19	$210.20	$210.20
Purchase #2	$160.55	8.150%	$173.6348	$173.63	$173.65	$173.60
Purchase #3	$221.93	7.167%	$237.8357	$237.84	$237.85	$237.80
Purchase #4	$28.75	9.298%	$31.4232	$31.42	$31.40	$31.40
Purchase #5	$168.39	10.166%	$185.5085	$185.51	$185.50	$185.50
Purchase #6	$68.85	13.581%	$78.2005	$78.20	$78.20	$78.20
Purchase #7	$153.95	3.777%	$159.7647	$159.76	$159.75	$159.80
7 purchase totals =	$1,000.03		$1,076.5612	$1,076.55	$1,076.55	$1,076.50