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	$208.91	3.702%	$216.6438	$216.64	$216.65	$216.60
Purchase #2	$105.41	5.240%	$110.9335	$110.93	$110.95	$110.90
Purchase #3	$223.38	7.616%	$240.3926	$240.39	$240.40	$240.40
Purchase #4	$53.72	7.106%	$57.5373	$57.54	$57.55	$57.50
Purchase #5	$107.37	11.329%	$119.5339	$119.53	$119.55	$119.50
Purchase #6	$101.89	3.673%	$105.6324	$105.63	$105.65	$105.60
Purchase #7	$238.90	3.250%	$246.6643	$246.66	$246.65	$246.70
7 purchase totals =	$1,039.58		$1,097.3378	$1,097.32	$1,097.40	$1,097.20