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	$245.60	11.796%	$274.571	$274.57	$274.55	$274.60
Purchase #2	$178.58	11.182%	$198.5488	$198.55	$198.55	$198.50
Purchase #3	$30.60	10.400%	$33.7824	$33.78	$33.80	$33.80
Purchase #4	$105.75	11.599%	$118.0159	$118.02	$118.00	$118.00
Purchase #5	$50.40	4.199%	$52.5163	$52.52	$52.50	$52.50
Purchase #6	$111.53	4.131%	$116.1373	$116.14	$116.15	$116.10
Purchase #7	$202.70	7.858%	$218.6282	$218.63	$218.65	$218.60
7 purchase totals =	$925.16		$1,012.1999	$1,012.21	$1,012.20	$1,012.10