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	$90.98	13.801%	$103.5361	$103.54	$103.55	$103.50
Purchase #2	$173.37	13.660%	$197.0523	$197.05	$197.05	$197.10
Purchase #3	$175.26	5.694%	$185.2393	$185.24	$185.25	$185.20
Purchase #4	$17.77	10.150%	$19.5737	$19.57	$19.55	$19.60
Purchase #5	$208.45	13.167%	$235.8966	$235.90	$235.90	$235.90
Purchase #6	$130.59	9.363%	$142.8171	$142.82	$142.80	$142.80
Purchase #7	$196.89	10.320%	$217.209	$217.21	$217.20	$217.20
7 purchase totals =	$993.31		$1,101.3241	$1,101.33	$1,101.30	$1,101.30