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	$96.55	8.423%	$104.6824	$104.68	$104.70	$104.70
Purchase #2	$172.37	5.204%	$181.3401	$181.34	$181.35	$181.30
Purchase #3	$77.58	9.782%	$85.1689	$85.17	$85.15	$85.20
Purchase #4	$246.88	10.764%	$273.4542	$273.45	$273.45	$273.50
Purchase #5	$249.37	10.817%	$276.3444	$276.34	$276.35	$276.30
Purchase #6	$40.45	12.241%	$45.4015	$45.40	$45.40	$45.40
Purchase #7	$185.71	9.604%	$203.5456	$203.55	$203.55	$203.50
7 purchase totals =	$1,068.91		$1,169.9371	$1,169.93	$1,169.95	$1,169.90