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	$147.73	11.603%	$164.8711	$164.87	$164.85	$164.90
Purchase #2	$183.70	4.189%	$191.3952	$191.40	$191.40	$191.40
Purchase #3	$99.94	11.460%	$111.3931	$111.39	$111.40	$111.40
Purchase #4	$96.93	11.172%	$107.759	$107.76	$107.75	$107.80
Purchase #5	$36.47	11.424%	$40.6363	$40.64	$40.65	$40.60
Purchase #6	$130.90	10.205%	$144.2583	$144.26	$144.25	$144.30
Purchase #7	$78.93	10.462%	$87.1877	$87.19	$87.20	$87.20
7 purchase totals =	$774.60		$847.5007	$847.51	$847.50	$847.60