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	$167.56	10.509%	$185.1689	$185.17	$185.15	$185.20
Purchase #2	$119.73	13.853%	$136.3162	$136.32	$136.30	$136.30
Purchase #3	$64.64	13.793%	$73.5558	$73.56	$73.55	$73.60
Purchase #4	$198.64	7.171%	$212.8845	$212.88	$212.90	$212.90
Purchase #5	$148.92	4.527%	$155.6616	$155.66	$155.65	$155.70
Purchase #6	$24.40	13.516%	$27.6979	$27.70	$27.70	$27.70
Purchase #7	$249.49	12.275%	$280.1149	$280.11	$280.10	$280.10
7 purchase totals =	$973.38		$1,071.3998	$1,071.40	$1,071.35	$1,071.50