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	$111.89	10.310%	$123.4259	$123.43	$123.45	$123.40
Purchase #2	$163.54	10.874%	$181.3233	$181.32	$181.30	$181.30
Purchase #3	$69.43	12.846%	$78.349	$78.35	$78.35	$78.30
Purchase #4	$153.93	3.532%	$159.3668	$159.37	$159.35	$159.40
Purchase #5	$236.29	4.630%	$247.2302	$247.23	$247.25	$247.20
Purchase #6	$163.40	7.670%	$175.9328	$175.93	$175.95	$175.90
Purchase #7	$77.36	10.588%	$85.5509	$85.55	$85.55	$85.60
7 purchase totals =	$975.84		$1,051.1789	$1,051.18	$1,051.20	$1,051.10