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	$187.78	11.649%	$209.6545	$209.65	$209.65	$209.70
Purchase #2	$75.26	4.207%	$78.4262	$78.43	$78.45	$78.40
Purchase #3	$55.78	8.855%	$60.7193	$60.72	$60.70	$60.70
Purchase #4	$180.72	3.134%	$186.3838	$186.38	$186.40	$186.40
Purchase #5	$187.48	11.427%	$208.9033	$208.90	$208.90	$208.90
Purchase #6	$124.50	9.286%	$136.0611	$136.06	$136.05	$136.10
Purchase #7	$214.51	8.768%	$233.3182	$233.32	$233.30	$233.30
7 purchase totals =	$1,026.03		$1,113.4664	$1,113.46	$1,113.45	$1,113.50