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	$168.69	3.500%	$174.5942	$174.59	$174.60	$174.60
Purchase #2	$38.36	9.860%	$42.1423	$42.14	$42.15	$42.10
Purchase #3	$91.99	13.636%	$104.5338	$104.53	$104.55	$104.50
Purchase #4	$192.30	6.360%	$204.5303	$204.53	$204.55	$204.50
Purchase #5	$155.54	13.548%	$176.6126	$176.61	$176.60	$176.60
Purchase #6	$156.36	6.189%	$166.0371	$166.04	$166.05	$166.00
Purchase #7	$221.58	6.856%	$236.7715	$236.77	$236.75	$236.80
7 purchase totals =	$1,024.82		$1,105.2218	$1,105.21	$1,105.25	$1,105.10