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	$249.75	13.785%	$284.178	$284.18	$284.20	$284.20
Purchase #2	$14.44	3.333%	$14.9213	$14.92	$14.90	$14.90
Purchase #3	$161.96	7.514%	$174.1297	$174.13	$174.15	$174.10
Purchase #4	$142.87	3.493%	$147.8604	$147.86	$147.85	$147.90
Purchase #5	$101.89	4.586%	$106.5627	$106.56	$106.55	$106.60
Purchase #6	$130.76	12.357%	$146.918	$146.92	$146.90	$146.90
Purchase #7	$238.42	4.265%	$248.5886	$248.59	$248.60	$248.60
7 purchase totals =	$1,040.09		$1,123.1587	$1,123.16	$1,123.15	$1,123.20