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	$207.83	3.470%	$215.0417	$215.04	$215.05	$215.00
Purchase #2	$59.42	12.855%	$67.0584	$67.06	$67.05	$67.10
Purchase #3	$233.55	3.248%	$241.1357	$241.14	$241.15	$241.10
Purchase #4	$37.40	5.705%	$39.5337	$39.53	$39.55	$39.50
Purchase #5	$100.76	12.152%	$113.0044	$113.00	$113.00	$113.00
Purchase #6	$219.89	7.464%	$236.3026	$236.30	$236.30	$236.30
Purchase #7	$175.61	7.389%	$188.5858	$188.59	$188.60	$188.60
7 purchase totals =	$1,034.46		$1,100.6623	$1,100.66	$1,100.70	$1,100.60