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	$56.50	3.362%	$58.3995	$58.40	$58.40	$58.40
Purchase #2	$164.65	9.526%	$180.3346	$180.33	$180.35	$180.30
Purchase #3	$88.35	13.563%	$100.3329	$100.33	$100.35	$100.30
Purchase #4	$222.39	6.243%	$236.2738	$236.27	$236.25	$236.30
Purchase #5	$191.50	3.337%	$197.8904	$197.89	$197.90	$197.90
Purchase #6	$54.60	9.828%	$59.9661	$59.97	$59.95	$60.00
Purchase #7	$178.76	5.853%	$189.2228	$189.22	$189.20	$189.20
7 purchase totals =	$956.75		$1,022.4201	$1,022.41	$1,022.40	$1,022.40