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	$200.43	11.209%	$222.8962	$222.90	$222.90	$222.90
Purchase #2	$212.39	8.488%	$230.4177	$230.42	$230.40	$230.40
Purchase #3	$29.40	10.373%	$32.4497	$32.45	$32.45	$32.40
Purchase #4	$223.40	10.771%	$247.4624	$247.46	$247.45	$247.50
Purchase #5	$91.46	10.860%	$101.3926	$101.39	$101.40	$101.40
Purchase #6	$62.36	13.696%	$70.9008	$70.90	$70.90	$70.90
Purchase #7	$86.83	10.864%	$96.2632	$96.26	$96.25	$96.30
7 purchase totals =	$906.27		$1,001.7826	$1,001.78	$1,001.75	$1,001.80