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	$249.42	8.526%	$270.6855	$270.69	$270.70	$270.70
Purchase #2	$26.71	7.869%	$28.8118	$28.81	$28.80	$28.80
Purchase #3	$86.37	3.430%	$89.3325	$89.33	$89.35	$89.30
Purchase #4	$148.94	12.702%	$167.8584	$167.86	$167.85	$167.90
Purchase #5	$78.26	4.568%	$81.8349	$81.83	$81.85	$81.80
Purchase #6	$181.56	3.365%	$187.6695	$187.67	$187.65	$187.70
Purchase #7	$37.38	4.710%	$39.1406	$39.14	$39.15	$39.10
7 purchase totals =	$808.64		$865.3332	$865.33	$865.35	$865.30