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	$231.53	3.607%	$239.8813	$239.88	$239.90	$239.90
Purchase #2	$174.33	4.331%	$181.8802	$181.88	$181.90	$181.90
Purchase #3	$232.36	4.116%	$241.9239	$241.92	$241.90	$241.90
Purchase #4	$70.88	8.378%	$76.8183	$76.82	$76.80	$76.80
Purchase #5	$75.58	13.810%	$86.0176	$86.02	$86.00	$86.00
Purchase #6	$108.29	7.482%	$116.3923	$116.39	$116.40	$116.40
Purchase #7	$98.52	13.230%	$111.5542	$111.55	$111.55	$111.60
7 purchase totals =	$991.49		$1,054.4678	$1,054.46	$1,054.45	$1,054.50