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	$195.98	8.424%	$212.4894	$212.49	$212.50	$212.50
Purchase #2	$90.85	12.480%	$102.1881	$102.19	$102.20	$102.20
Purchase #3	$124.31	5.480%	$131.1222	$131.12	$131.10	$131.10
Purchase #4	$83.84	3.489%	$86.7652	$86.77	$86.75	$86.80
Purchase #5	$147.72	13.459%	$167.6016	$167.60	$167.60	$167.60
Purchase #6	$123.72	11.207%	$137.5853	$137.59	$137.60	$137.60
Purchase #7	$102.78	4.715%	$107.6261	$107.63	$107.65	$107.60
7 purchase totals =	$869.20		$945.3779	$945.39	$945.40	$945.40