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	$246.75	4.604%	$258.1104	$258.11	$258.10	$258.10
Purchase #2	$174.53	6.574%	$186.0036	$186.00	$186.00	$186.00
Purchase #3	$95.40	5.294%	$100.4505	$100.45	$100.45	$100.50
Purchase #4	$153.96	13.541%	$174.8077	$174.81	$174.80	$174.80
Purchase #5	$42.77	8.855%	$46.5573	$46.56	$46.55	$46.60
Purchase #6	$92.58	13.664%	$105.2301	$105.23	$105.25	$105.20
Purchase #7	$39.76	9.188%	$43.4131	$43.41	$43.40	$43.40
7 purchase totals =	$845.75		$914.5727	$914.57	$914.55	$914.60