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	$190.74	7.735%	$205.4937	$205.49	$205.50	$205.50
Purchase #2	$141.98	12.219%	$159.3285	$159.33	$159.35	$159.30
Purchase #3	$65.55	10.493%	$72.4282	$72.43	$72.45	$72.40
Purchase #4	$223.49	8.782%	$243.1169	$243.12	$243.10	$243.10
Purchase #5	$82.90	6.628%	$88.3946	$88.39	$88.40	$88.40
Purchase #6	$246.97	4.658%	$258.4739	$258.47	$258.45	$258.50
Purchase #7	$217.88	9.505%	$238.5895	$238.59	$238.60	$238.60
7 purchase totals =	$1,169.51		$1,265.8253	$1,265.82	$1,265.85	$1,265.80