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	$211.89	13.426%	$240.3384	$240.34	$240.35	$240.30
Purchase #2	$62.34	9.553%	$68.2953	$68.30	$68.30	$68.30
Purchase #3	$247.71	5.725%	$261.8914	$261.89	$261.90	$261.90
Purchase #4	$230.71	6.409%	$245.4962	$245.50	$245.50	$245.50
Purchase #5	$156.69	13.644%	$178.0688	$178.07	$178.05	$178.10
Purchase #6	$82.88	9.213%	$90.5157	$90.52	$90.50	$90.50
Purchase #7	$86.31	4.633%	$90.3087	$90.31	$90.30	$90.30
7 purchase totals =	$1,078.53		$1,174.9145	$1,174.93	$1,174.90	$1,174.90