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	$118.50	4.130%	$123.3941	$123.39	$123.40	$123.40
Purchase #2	$62.59	5.621%	$66.1082	$66.11	$66.10	$66.10
Purchase #3	$232.98	11.832%	$260.5462	$260.55	$260.55	$260.50
Purchase #4	$124.69	6.784%	$133.149	$133.15	$133.15	$133.10
Purchase #5	$92.64	6.363%	$98.5347	$98.53	$98.55	$98.50
Purchase #6	$144.38	13.724%	$164.1947	$164.19	$164.20	$164.20
Purchase #7	$18.35	11.146%	$20.3953	$20.40	$20.40	$20.40
7 purchase totals =	$794.13		$866.3222	$866.32	$866.35	$866.20