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	$187.59	4.801%	$196.5962	$196.60	$196.60	$196.60
Purchase #2	$154.32	3.110%	$159.1194	$159.12	$159.10	$159.10
Purchase #3	$202.76	11.309%	$225.6901	$225.69	$225.70	$225.70
Purchase #4	$197.48	9.321%	$215.8871	$215.89	$215.90	$215.90
Purchase #5	$138.76	4.730%	$145.3233	$145.32	$145.30	$145.30
Purchase #6	$167.44	4.193%	$174.4608	$174.46	$174.45	$174.50
Purchase #7	$231.87	3.597%	$240.2104	$240.21	$240.20	$240.20
7 purchase totals =	$1,280.22		$1,357.2873	$1,357.29	$1,357.25	$1,357.30