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	$156.35	6.817%	$167.0084	$167.01	$167.00	$167.00
Purchase #2	$124.93	6.680%	$133.2753	$133.28	$133.30	$133.30
Purchase #3	$57.58	11.488%	$64.1948	$64.19	$64.20	$64.20
Purchase #4	$69.64	12.697%	$78.4822	$78.48	$78.50	$78.50
Purchase #5	$178.54	6.359%	$189.8934	$189.89	$189.90	$189.90
Purchase #6	$184.25	5.712%	$194.7744	$194.77	$194.75	$194.80
Purchase #7	$154.53	3.191%	$159.4611	$159.46	$159.45	$159.50
7 purchase totals =	$925.82		$987.0896	$987.08	$987.10	$987.20