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	$222.94	8.238%	$241.3058	$241.31	$241.30	$241.30
Purchase #2	$58.65	4.292%	$61.1673	$61.17	$61.15	$61.20
Purchase #3	$249.32	8.766%	$271.1754	$271.18	$271.20	$271.20
Purchase #4	$101.54	7.594%	$109.2509	$109.25	$109.25	$109.30
Purchase #5	$76.25	5.409%	$80.3744	$80.37	$80.35	$80.40
Purchase #6	$73.85	6.626%	$78.7433	$78.74	$78.75	$78.70
Purchase #7	$167.27	13.394%	$189.6741	$189.67	$189.65	$189.70
7 purchase totals =	$949.82		$1,031.6912	$1,031.69	$1,031.65	$1,031.80