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	$121.74	7.767%	$131.1955	$131.20	$131.20	$131.20
Purchase #2	$184.86	8.619%	$200.7931	$200.79	$200.80	$200.80
Purchase #3	$33.56	11.299%	$37.3519	$37.35	$37.35	$37.40
Purchase #4	$184.59	6.408%	$196.4185	$196.42	$196.40	$196.40
Purchase #5	$183.99	4.557%	$192.3744	$192.37	$192.35	$192.40
Purchase #6	$56.30	13.326%	$63.8025	$63.80	$63.80	$63.80
Purchase #7	$204.58	10.129%	$225.3019	$225.30	$225.30	$225.30
7 purchase totals =	$969.62		$1,047.2378	$1,047.23	$1,047.20	$1,047.30