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	$63.30	12.225%	$71.0384	$71.04	$71.05	$71.00
Purchase #2	$84.55	5.567%	$89.2569	$89.26	$89.25	$89.30
Purchase #3	$147.30	13.671%	$167.4374	$167.44	$167.45	$167.40
Purchase #4	$216.89	13.575%	$246.3328	$246.33	$246.35	$246.30
Purchase #5	$248.32	8.287%	$268.8983	$268.90	$268.90	$268.90
Purchase #6	$245.58	4.711%	$257.1493	$257.15	$257.15	$257.10
Purchase #7	$79.33	12.784%	$89.4715	$89.47	$89.45	$89.50
7 purchase totals =	$1,085.27		$1,189.5846	$1,189.59	$1,189.60	$1,189.50