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	$32.33	10.192%	$35.6251	$35.63	$35.65	$35.60
Purchase #2	$196.99	9.266%	$215.2431	$215.24	$215.25	$215.20
Purchase #3	$52.25	10.287%	$57.625	$57.63	$57.65	$57.60
Purchase #4	$61.34	10.276%	$67.6433	$67.64	$67.65	$67.60
Purchase #5	$186.53	5.259%	$196.3396	$196.34	$196.35	$196.30
Purchase #6	$174.55	12.579%	$196.5066	$196.51	$196.50	$196.50
Purchase #7	$225.25	9.250%	$246.0856	$246.09	$246.10	$246.10
7 purchase totals =	$929.24		$1,015.0683	$1,015.08	$1,015.15	$1,014.90